Given:
[tex]\begin{gathered} a^2-7a-8 \\ a=-2 \end{gathered}[/tex]
Solution:
To evaluate the expression, we will substitute the value of -2 to a.
[tex]\begin{gathered} a^2-7a-8 \\ a=-2 \\ (-2)^2-7(-2)-8 \\ \end{gathered}[/tex]
Now that we have substituted -2, we will perform the operations in between.
Since we are given a quadratic equation, we have to deal with the exponent.
Negative to raise to two is also equal to -2 multiplied by itself.
We will have:
[tex]=(-2)\cdot(-2)^{}-7(-2)-8[/tex]
A negative number multiplied by another negative number will become a positive number.
Negative 2 multiplied by negative 2 is equal to positive 4.
[tex]=4-7(-2)-8[/tex]
Now, for -7a we will have -2 multiplied by negative 7. It will become positive 14.
[tex]\begin{gathered} =4-7(-2)-8 \\ =4+14-8 \end{gathered}[/tex]
After that, we will add 4 and 14 then subtract -8.
[tex]\begin{gathered} =4+14-8 \\ =18-8 \\ =10 \end{gathered}[/tex]
ANSWER: 10
