Intermediate Geometry : Intermediate Geometry

Study concepts, example questions & explanations for Intermediate Geometry

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Example Questions

Example Question #1 : How To Find The Equation Of A Line

Write the equation for a line that passes through the points \(\displaystyle (3,2)\) and \(\displaystyle (2,-1)\).

Possible Answers:

\(\displaystyle y = \frac{1}{3}x - 13\)

\(\displaystyle y = 5x -13\)

\(\displaystyle y = \frac{1}{3}x + 1\)

\(\displaystyle y = x-3\)

\(\displaystyle y = x + 1\)

Correct answer:

\(\displaystyle y = \frac{1}{3}x + 1\)

Explanation:

To determine the equation, first find the slope:

\(\displaystyle \frac{\Delta y}{\Delta x} = \frac{3-2}{2--1} = \frac{1 }{3 }\)

We want this equation in slope-intercept form, \(\displaystyle y = mx+b\). We know \(\displaystyle x\) and \(\displaystyle y\) because we have two coordinate pairs to choose from representing an \(\displaystyle x\) and a \(\displaystyle y\). We know \(\displaystyle m\) because that represents the slope. We just need to solve for \(\displaystyle b\), and then we can write the equation.

We can choose either point and get the correct answer. Let's choose \(\displaystyle (3,2)\)

\(\displaystyle 2= \frac{1}{3} (3) + b\) multiply "\(\displaystyle mx\)"

\(\displaystyle 2 = 1 + b\) subtract \(\displaystyle 1\) from both sides

\(\displaystyle 1 = b\)

This means that the \(\displaystyle y = mx+b\) form is \(\displaystyle y = \frac{1}{3}x +1\)

Example Question #2 : How To Find The Equation Of A Line

Find the equation for a line passing through the points \(\displaystyle (5, -1)\) and \(\displaystyle (3,-7)\).

Possible Answers:

\(\displaystyle y = 3x + 2\)

\(\displaystyle y = \frac{1}{3}x -6\)

\(\displaystyle y = 3x-16\)

\(\displaystyle y = \frac{1}{3} x -8\)

\(\displaystyle y = -3x +14\)

Correct answer:

\(\displaystyle y = 3x-16\)

Explanation:

To determine the equation, first find the slope:

\(\displaystyle \frac{\Delta y}{\Delta x} = \frac{-7--1}{3-5} = \frac{-6 }{-2 } =3\)

We want this equation in slope-intercept form, \(\displaystyle y = mx+b\). We know \(\displaystyle x\) and \(\displaystyle y\) because we have two coordinate pairs to choose from representing an \(\displaystyle x\) and a \(\displaystyle y\) . We know \(\displaystyle m\) because that represents the slope. We just need to solve for \(\displaystyle b\), and then we can write the equation.

We can choose either point and get the correct answer. Let's choose \(\displaystyle (3, -7)\)

\(\displaystyle -7 = 3 (3) + b\) multiply "\(\displaystyle mx\)"

\(\displaystyle -7 =9+ b\) subtract \(\displaystyle 6\) from both sides

\(\displaystyle -16 = b\)

This means that the \(\displaystyle y = mx+b\) form is \(\displaystyle y = 3x -16\)

Example Question #2 : How To Find The Equation Of A Line

Find the equation for the line passing through the points \(\displaystyle (6,2)\) and \(\displaystyle (-3,-4)\).

Possible Answers:

\(\displaystyle y = \frac{2}{3}x - 2\)

\(\displaystyle y =- \frac{2}{3}x + 6\)

\(\displaystyle y = \frac{2}{3} x + 2\)

\(\displaystyle y = 2x+2\)

\(\displaystyle y = 2x - 2\)

Correct answer:

\(\displaystyle y = \frac{2}{3}x - 2\)

Explanation:

To determine the equation, first find the slope:

\(\displaystyle \frac{\Delta y}{\Delta x} = \frac{2--4}{6--3} = \frac{6}{9 } =\frac{2}{3}\)

We want this equation in slope-intercept form, \(\displaystyle y = mx+b\). We know \(\displaystyle x\) and \(\displaystyle y\) because we have two coordinate pairs to choose from representing an \(\displaystyle x\) and a \(\displaystyle y\). We know \(\displaystyle m\) because that represents the slope. We just need to solve for \(\displaystyle b\), and then we can write the equation.

We can choose either point and get the correct answer. Let's choose \(\displaystyle (6, 2)\)

\(\displaystyle 2 = \frac{2}{3} (6) + b\) multiply "\(\displaystyle mx\)"

\(\displaystyle 2 = 4 + b\) subtract \(\displaystyle 4\) from both sides

\(\displaystyle -2 = b\)

This means that the \(\displaystyle y = mx+b\) form is \(\displaystyle y = \frac{2}{3}x-2\)

Example Question #101 : Lines

Find the equation for the line passing through the points \(\displaystyle (5, 7)\) and \(\displaystyle (2, 3 )\).

Possible Answers:

\(\displaystyle y = \frac{7}{4} x + \frac{1}{2 }\)

\(\displaystyle y = \frac{3}{4} x + \frac{3}{2}\)

\(\displaystyle y = \frac{10}{3} x - \frac{11}{3}\)

\(\displaystyle y = \frac{4}{7 } x + 1\)

\(\displaystyle y = \frac{4}{3} x + \frac{1}{3 }\)

Correct answer:

\(\displaystyle y = \frac{4}{3} x + \frac{1}{3 }\)

Explanation:

First, determine the slope of the line using the slope formula:

\(\displaystyle \frac{ \Delta y }{ \Delta x } = \frac{ y_2 - y_1 }{ x _ 2 - x_1 } = \frac{7 - 3} { 5 - 2 } = \frac{4}{3}\)

The equation will be in the form \(\displaystyle y = mx + b\) where m is the slope that we just determined, and b is the y-intercept. To determine that, we can plug in the slope for m and the coordinates of one of the original points for x and y:

\(\displaystyle 3 = \frac{4}{3} (2) + b\)

\(\displaystyle 3 = \frac{8 }{3 } + b\) to subtract, it will be easier to convert 3 to a fraction, \(\displaystyle \frac{9}{3}\)

\(\displaystyle \frac{9}{3} - \frac{8}{3} = b\)

\(\displaystyle \frac{1}{3} = b\)

The equation is \(\displaystyle y = \frac{4}{3} x + \frac{1}{3}\)

Example Question #1391 : Intermediate Geometry

Write the equation for the line passing through the points \(\displaystyle (4, 2)\) and \(\displaystyle (-2,1)\).

Possible Answers:

\(\displaystyle y = \frac{1}{6} x + 1 \frac{1}{3 }\)

\(\displaystyle y = \frac{1}{2} x + 2\)

\(\displaystyle y = \frac{1}{2} x\)

\(\displaystyle y = x + 3\)

\(\displaystyle y = \frac{1}{6} x + \frac{2}{3}\)

Correct answer:

\(\displaystyle y = \frac{1}{6} x + 1 \frac{1}{3 }\)

Explanation:

First, find the slope of the line:

\(\displaystyle \frac{ \Delta y }{ \Delta x } = \frac{2 - 1 }{ 4 - - 2 } = \frac{ 1 }{ 6 }\)

Now we want to find the y-intercept. We can figure this out by plugging in the slope for "m" and one of the points in for x and y in the formula \(\displaystyle y = mx+b\):

\(\displaystyle 1 = \frac{1}{6} (-2 ) + b\)

\(\displaystyle 1 = -\frac{1}{3} + b\)

\(\displaystyle 1 \frac{1}{3} = b\)

The equation is \(\displaystyle y = \frac{ 1}{6} x + 1 \frac{1}{3}\)

Example Question #111 : Coordinate Geometry

Find the equation of a line passing through the points \(\displaystyle (0,-5)\) and \(\displaystyle (5,0)\).

Possible Answers:

None of these.

\(\displaystyle y=-x-5\)

\(\displaystyle y=-x+5\)

\(\displaystyle y=x+5\)

\(\displaystyle y=x-5\)

Correct answer:

\(\displaystyle y=x-5\)

Explanation:

To find the equation of a line passing through these points we must find a line with that same slope. Start by finding the slope between the two points and then use the point slope equation to find the equation of the line.

slope:

\(\displaystyle m=\frac{y_{2}-y_{1}}{x_{2}-x_{1}}=\frac{0--5}{5-0}=1\)

Now use the point slope equation:

\(\displaystyle y-y_{1}=m(x-x_{1})\rightarrow y-(-5)=1(x-0)\rightarrow \mathbf{y=x-5}\)

*make sure you use the SAME coordinate pair when substituting x and y into the point slope equation.

Example Question #112 : Lines

Find the equation of a line that goes through the points \(\displaystyle (3, 12)\) and \(\displaystyle (-2, 5)\).

Possible Answers:

\(\displaystyle y=-\frac{2}{5}x-\frac{11}{5}\)

\(\displaystyle y=-\frac{1}{6}x-\frac{6}{5}\)

\(\displaystyle y=\frac{7}{5}x+\frac{39}{5}\)

\(\displaystyle y=\frac{2}{3}x+\frac{4}{9}\)

Correct answer:

\(\displaystyle y=\frac{7}{5}x+\frac{39}{5}\)

Explanation:

Recall that the slope-intercept form of a line:

\(\displaystyle y=mx+b\),

where \(\displaystyle m=\text{slope}\) and \(\displaystyle b=\text{y-intercept}\).

First, find the slope of the line by using the following formula:

\(\displaystyle \text{Slope of Line}=\frac{y_2-y_1}{x_2-x_1}\)

\(\displaystyle \text{Slope}=\frac{5-12}{-2-3}=\frac{7}{5}\)

Next, find the y-intercept of the line by plugging in \(\displaystyle 1\) of the points into the semi-completed formula.

\(\displaystyle y=\frac{7}{5}x+b\)

Plugging in \(\displaystyle (3, 12)\) yields the following:

\(\displaystyle 12=\frac{7}{5}(3)+b\)

Solve for \(\displaystyle b\).

\(\displaystyle b+\frac{21}{5}=12\)

\(\displaystyle b=\frac{39}{5}\)

The equation of the line is then \(\displaystyle y=\frac{7}{5}x+\frac{39}{5}\).

 

Example Question #113 : Lines

Find the equation of a line that goes through the points \(\displaystyle (-10, 7)\) and \(\displaystyle (12, 8)}\).

Possible Answers:

\(\displaystyle y=\frac{5}{18}x+\frac{1}{9}\)

\(\displaystyle y=\frac{1}{22}x+\frac{82}{11}\)

\(\displaystyle y=-\frac{18}{19}x-\frac{6}{19}\)

\(\displaystyle y=22x+5\)

Correct answer:

\(\displaystyle y=\frac{1}{22}x+\frac{82}{11}\)

Explanation:

Recall that the slope-intercept form of a line:

\(\displaystyle y=mx+b\),

where \(\displaystyle m=\text{slope}\) and \(\displaystyle b=\text{y-intercept}\).

First, find the slope of the line by using the following formula:

\(\displaystyle \text{Slope of Line}=\frac{y_2-y_1}{x_2-x_1}\)

\(\displaystyle \text{Slope}=\frac{8-7}{12-(-10)}=\frac{1}{22}\)

Next, find the y-intercept of the line by plugging in \(\displaystyle 1\) of the points into the semi-completed formula.

\(\displaystyle y=\frac{1}{22}x+b\)

Plugging in \(\displaystyle (12, 8)\) yields the following:

\(\displaystyle 8=\frac{1}{22}(12)+b\)

Solve for \(\displaystyle b\).

\(\displaystyle b+\frac{6}{11}=8\)

\(\displaystyle b=\frac{82}{11}\)

The equation of the line is then \(\displaystyle y=\frac{1}{22}x+\frac{82}{11}\).

 

Example Question #1392 : Intermediate Geometry

Find the equation of a line that goes through the points \(\displaystyle (16, 10)\) and \(\displaystyle (15, 2)\).

Possible Answers:

\(\displaystyle y=4x+108\)

\(\displaystyle y=\frac{1}{8}x+112\)

\(\displaystyle y=8x-118\)

\(\displaystyle y=-\frac{1}{4}x-111\)

Correct answer:

\(\displaystyle y=8x-118\)

Explanation:

Recall that the slope-intercept form of a line:

\(\displaystyle y=mx+b\),

where \(\displaystyle m=\text{slope}\) and \(\displaystyle b=\text{y-intercept}\).

First, find the slope of the line by using the following formula:

\(\displaystyle \text{Slope of Line}=\frac{y_2-y_1}{x_2-x_1}\)

\(\displaystyle \text{Slope}=\frac{10-2}{16-15}=8\)

Next, find the y-intercept of the line by plugging in \(\displaystyle 1\) of the points into the semi-completed formula.

\(\displaystyle y=8x+b\)

Plugging in \(\displaystyle (16, 10)\) yields the following:

\(\displaystyle 10=8(16)+b\)

Solve for \(\displaystyle b\).

\(\displaystyle b+128=10\)

\(\displaystyle b=-118\)

The equation of the line is then \(\displaystyle y=8x-118\).

 

Example Question #1393 : Intermediate Geometry

Find the equation of a line that goes through the points \(\displaystyle (-3, -5)\) and \(\displaystyle (-4, 8)\).

Possible Answers:

\(\displaystyle y=-\frac{2}{13}x-\frac{16}{13}\)

\(\displaystyle y=-12x+32\)

\(\displaystyle y=-17x-29\)

\(\displaystyle y=-13x-44\)

Correct answer:

\(\displaystyle y=-13x-44\)

Explanation:

Recall that the slope-intercept form of a line:

\(\displaystyle y=mx+b\),

where \(\displaystyle m=\text{slope}\) and \(\displaystyle b=\text{y-intercept}\).

First, find the slope of the line by using the following formula:

\(\displaystyle \text{Slope of Line}=\frac{y_2-y_1}{x_2-x_1}\)

\(\displaystyle \text{Slope}=\frac{8-(-5)}{-4-(-3)}=-13\)

Next, find the y-intercept of the line by plugging in \(\displaystyle 1\) of the points into the semi-completed formula.

\(\displaystyle y=-13x+b\)

Plugging in \(\displaystyle (-3, -5)\) yields the following:

\(\displaystyle -5=-13(-3)+b\)

Solve for \(\displaystyle b\).

\(\displaystyle b+39=-5\)

\(\displaystyle b=-44\)

The equation of the line is then \(\displaystyle y=-13x-44\).

 

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