Question

question 7
given ( f(x) = -3x^2 - x - 15 ), find ( f(-8) )

Explanation:

Step1: Substitute \( x = -8 \) into the function \( f(x) \)

We have \( f(x) = -3x^2 - x - 15 \), so when \( x = -8 \), we substitute it into each term. First, calculate \( x^2 \): \( (-8)^2 = 64 \). Then the first term \( -3x^2 \) becomes \( -3\times64 \), the second term \( -x \) becomes \( -(-8)=8 \), and the third term is \( -15 \). So the expression becomes \( f(-8)=-3\times(-8)^2-(-8)-15 \).

Step2: Calculate each term

First, calculate \( -3\times(-8)^2 \): \( (-8)^2 = 64 \), so \( -3\times64=-192 \). Then, \( -(-8)=8 \). Now we substitute these back into the expression: \( f(-8)=-192 + 8 - 15 \).

Step3: Simplify the expression

First, add \( -192 \) and \( 8 \): \( -192 + 8=-184 \). Then, subtract \( 15 \) from \( -184 \): \( -184 - 15=-199 \).

Answer:

\( -199 \)