ACT Math : How to use the grid method for FOIL

Study concepts, example questions & explanations for ACT Math

varsity tutors app store varsity tutors android store varsity tutors ibooks store

Example Questions

Example Question #1 : How To Use The Grid Method For Foil

The expression \displaystyle (2x+4)(9-x) is equivalent to:

Possible Answers:

\displaystyle 2x^2-14x-36

\displaystyle -2x^2+14x+36

\displaystyle x^2+14x+36

\displaystyle -2x^2+22x+36

\displaystyle 2x^2+14x+36

Correct answer:

\displaystyle -2x^2+14x+36

Explanation:

Use the grid method to FOIL.

Foil

Combine the like terms.

Example Question #2 : How To Use The Grid Method For Foil

Which of the following is the product of \displaystyle (3a^3+6)(a^3-5)?

Possible Answers:

\displaystyle 3a^6+21a^3-30

\displaystyle 3a^6+9a^3-30

\displaystyle 3a^6-9a^3-30

\displaystyle 3a^6-21^3-30

\displaystyle 3a^6-30

Correct answer:

\displaystyle 3a^6-9a^3-30

Explanation:

Using FOIL which stands for the multiplication process between the Firsts, Outers, Inners, and Lasts, we end up with the expression 

\displaystyle 3a^6-15a^3+6a^3-30.

From there, combine the like terms \displaystyle -15a^3+6a^3 to get \displaystyle -9a^3.

Therefore the product becomes,

\displaystyle 3a^6-9a^3-30

Example Question #2 : How To Use The Grid Method For Foil

The expression \displaystyle (4x-2)(x+3) is equivalent to __________.

Possible Answers:

\displaystyle 4x^2+10x-1

\displaystyle 4x^2+10x+6

\displaystyle 4x^2+10x-6

\displaystyle 4x^2-10x-6

\displaystyle -4x^2+10x-6

Correct answer:

\displaystyle 4x^2+10x-6

Explanation:

This question is asking you to multiply two binomials. You can use the grid method for FOIL.

Foil

Learning Tools by Varsity Tutors