Solve by factoring the trinomial as a binomial square and then use the square root method. Round to the nearest tenth if necessary.

x2 + 16x + 64 = 81
A. {9, -9}
B. {-8, 9}
C. {-17, 1}
D. no real solution

Question

Solve by factoring the trinomial as a binomial square and then use the square root method. Round to the nearest tenth if necessary.

x2 + 16x + 64 = 81
	A.	{9, -9}
	B.	{-8, 9}
	C.	{-17, 1}
	D.	no real solution

mathteacher1729 · Answer

We can use the fact that the "Difference of squares" (google it) :) is 
$x^2-a^2=(x+a)(x-a)$ ?  In this case $a^2=64 \Rightarrow a = 8$.

anonymous · Answer

$$(x+8)^2=81$$
$$x+8=9\text { or } x+8=-9$$
$$x=1 , \text { or } x = -17$$

anonymous · Answer

factor 
$$x^2+16x+64$$ as 
$$(x+8)(x+8)=(x+8)^2$$ because 
$$64=8^2\text { and } 16=2\times 8$$