Evaluate 3x 2power - 4x -9 for x= -5

Answer 1

To evaluate the expression \(3x^2 - 4x - 9\) for \(x = -5\), we will substitute \(-5\) into the expression and then simplify.

1. Substitute \(-5\) for \(x\):

\[ 3(-5)^2 - 4(-5) - 9 \]

2. Calculate \((-5)^2\):

\[ (-5)^2 = 25 \]

3. Multiply by \(3\):

\[ 3 \times 25 = 75 \]

4. Calculate \(-4(-5)\):

\[ -4(-5) = 20 \]

5. Combine all parts:

\[ 75 + 20 - 9 \]

6. Add \(75\) and \(20\):

\[ 75 + 20 = 95 \]

7. Subtract \(9\):

\[ 95 - 9 = 86 \]

So, the value of the expression \(3x^2 - 4x - 9\) when \(x = -5\) is \(\boxed{86}\).