Question

Evaluate the expression when x= -6. x² + 8x-9

Answer 1

Answer:

-21.

Step-by-step explanation:

Evaluating an expression is very similar to solving an equation, just without an equal sign.

Start by plugging in the given x value into your expression

$x^{2} +8x-9$

to

$(-6)^{2} +8(-6)-9$

Because a negative multiplied by another negative or itself cancels the negatives out, $(-6)^{2}$ and $6^{2}$ are the same when evaluated**.

$36+8(-6)-9$

Positive times negative makes negative, so $8(-6)$ is $-48$, which leaves

$36-48-9$

Then by simplifying, you get

$-12-9$

and finally

$-21$

Hope this helped!

**Be careful though, because $(-6)^{2}$ and $-6^{2}$ are not the same thing. $-6^{2}$ is read as $-(6)^{2}$, which implies that you're squaring 6, but the ending value is negative.

Answer 2

-21 is the answer :)