Factor.
-$49 - 126 x + 81 x ^ { 2 }$
A) $( 81 x - 7 ) ( x - 7 )$
B) $( 9 x + 7 ) ^ { 2 }$
C) $( 9 x - 7 ) ^ { 2 }$
D) Prime

Question

Quizplus · Accepted Answer

This expression is a perfect square trinomial of the form $(ax+b)^2 = a^2x^2+2abx+b^2$. We can see that $81x^2$ is the square of $9x$, and $49$ is the square of $7$. Furthermore, we can write $-126x$ as $2(9x)(-7)$. Therefore, using the formula, we have:
\begin{align*}
49 - 126 x + 81 x ^ { 2 } &= (9x)^2-2(9x)(7)+7^2\
&=(9x-7)^2
\end{align*}
Thus, the answer is choice C.

Factor - 49−126x+81x249 - 126 x + 81 x ^ { 2 }49−126x+81x2

Factor
- $49 - 126 x + 81 x ^ { 2 }$