Multiply.
-$\left( 11 + \frac { 1 } { 9 } z \right) \left( 11 - \frac { 1 } { 9 } z \right)$
A) $121 - \frac { 1 } { 81 } z ^ { 2 }$
B) $121 - \frac { 2 } { 9 } z ^ { 2 }$
C) $121 + \frac { 22 } { 9 } z - \frac { 1 } { 81 } z ^ { 2 }$
D) $121 - \frac { 22 } { 9 } z - \frac { 1 } { 81 } z ^ { 2 }$

Question

Quizplus · Accepted Answer

This is a classic example of the difference of squares formula, $a^2 - b^2 = (a + b)(a - b)$, where $a = 11$ and $b = \frac{1}{9}z$. Squaring $a$ gives $121$ and squaring $b$ gives $\frac{1}{81}z^2$, hence $121 - \frac{1}{81}z^2$.

Multiply - (11+19z)(11−19z)\left( 11 + \frac { 1 } { 9 } z \right) \left( 11 - \frac { 1 } { 9 } z \right)(11+91​z)(11−91​z)

Multiply
- $\left( 11 + \frac { 1 } { 9 } z \right) \left( 11 - \frac { 1 } { 9 } z \right)$