5. Factor
y^2 - 64
A) (y + 64)(y - 64)
(y + 8)(y - 8)
C) (y^2 + 8)(y^2 - 8)
D) (y - 8)(y - 8)
A little help with my kid's homework please.
B
When expanding brackets, use the FOIL method, which stands for First, Outer, Inner, Last.
First: y * y = y^2
Outer: y * (-8) = -8y
Inner: y * 8 = 8y
Last: 8 * (-8) = -64
The 8y and the -8y cancel each other out to get 0, and therefore your answer is B.
difference of squares
y^2 - (64)--------> square root it (root)64 = +- 8
with (y - a)(y+a) = 0,
substitute the numbers:
so the answer is (y + 8)(y - 8)
B (y + 8)(y - 8)
This is a perfect sqare with no middle term. Both factors are the same but one is positive and one is negative.
(y + 8)(y - 8)
Comments
B
When expanding brackets, use the FOIL method, which stands for First, Outer, Inner, Last.
First: y * y = y^2
Outer: y * (-8) = -8y
Inner: y * 8 = 8y
Last: 8 * (-8) = -64
The 8y and the -8y cancel each other out to get 0, and therefore your answer is B.
difference of squares
y^2 - (64)--------> square root it (root)64 = +- 8
with (y - a)(y+a) = 0,
substitute the numbers:
so the answer is
(y + 8)(y - 8)
B (y + 8)(y - 8)
This is a perfect sqare with no middle term. Both factors are the same but one is positive and one is negative.