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Example Questions
Example Question #5 : Linear Equations With Whole Numbers
What is the solution of for the two systems?
We first multiply the second equation by 4.
So our resulting equation is:
Then we subtract the first equation from the second new equation.
Left Hand Side:
Right Hand Side:
Resulting Equation:
We divide both sides by -15
Left Hand Side:
Right Hand Side:
Our result is:
Example Question #12 : How To Find The Solution For A System Of Equations
Find the solutions for the following set of equations:
If we multiply both sides of our bottom equation by , we get
. We can now add our two equations, and eliminate
, leaving only one variable. When we add the equations, we get
. Therefore,
. Finally, we go back to either of our equations, and plug in
so we can solve for
.
Example Question #11 : How To Find The Solution For A System Of Equations
Give the solution to the system of equations below.
No solution
Solve the second equation for , allowing us to solve using the substitution method.
Substitute for in the first equation, and solve for
.
Now, substitute for in either equation; we will choose the second. This allows us to solve for
.
Now we can write the solution in the notation , or
.
Example Question #1 : Inequalities
|12x + 3y| < 15
What is the range of values for y, expressed in terms of x?
y < 5 – 4x
5 + 4x < y < 5 – 4x
–5 – 4x < y < 5 – 4x
5 – 4x < y < 5 + 4x
y > 15 – 12x
–5 – 4x < y < 5 – 4x
Recall that with absolute values and "less than" inequalities, we have to hold the following:
12x + 3y < 15
AND
12x + 3y > –15
Otherwise written, this is:
–15 < 12x + 3y < 15
In this form, we can solve for y. First, we have to subtract x from all 3 parts of the inequality:
–15 – 12x < 3y < 15 – 12x
Now, we have to divide each element by 3:
(–15 – 12x)/3 < y < (15 – 12x)/3
This simplifies to:
–5 – 4x < y < 5 – 4x
Example Question #2 : Inequalities
|4x + 14| > 30
What is a possible valid value of x?
1
7
–3
–11
4
7
This inequality could be rewritten as:
4x + 14 > 30 OR 4x + 14 < –30
Solve each for x:
4x + 14 > 30; 4x > 16; x > 4
4x + 14 < –30; 4x < –44; x < –11
Therefore, anything between –11 and 4 (inclusive) will not work. Hence, the answer is 7.
Example Question #781 : Psat Mathematics
Given the inequality, |2x – 2| > 20,
what is a possible value for x?
11
–10
–8
0
10
–10
For this problem, we must take into account the absolute value.
First, we solve for 2x – 2 > 20. But we must also solve for 2x – 2 < –20 (please notice that we negate 20 and we also flip the inequality sign).
First step:
2x – 2 > 20
2x > 22
x > 11
Second step:
2x – 2 < –20
2x < –18
x < –9
Therefore, x > 11 and x < –9.
A possible value for x would be –10 since that is less than –9.
Note: the value 11 would not be a possible value for x because the inequality sign given does not include an equal sign.
Example Question #782 : Psat Mathematics
Solve for .
Move +5 using subtraction rule which will give you.
Divide both sides by 2 (using division rule) and you will get which is the same as
Example Question #5 : Inequalities
If , which of the following MUST be true?
I.
II.
III.
I, II, and III
I only
III only
I and II only
II only
I only
Subtract 5 from both sides of the inequality:
Multiply both sides by 5:
Therefore only I must be true.
Example Question #783 : Psat Mathematics
Which of the following is equivalent to ?
Solve for both x – 3 < 2 and –(x – 3) < 2.
x – 3 < 2 and –x + 3 < 2
x < 2 + 3 and –x < 2 – 3
x < 5 and –x < –1
x < 5 and x > 1
The results are x < 5 and x > 1.
Combine the two inequalities to get 1 < x < 5
Example Question #41 : Equations / Inequalities
Which of the following is a possible set of solutions to ?
Manipulate the inequality until is on a side by itself:
For this equation, must be less than 6. Find the answer choice with values all less than 6. In this case, it will be -1, 4, and 5.
All PSAT Math Resources
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