Question

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

Answers

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Answered by GPT-4o mini
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 \(\boxed{86}\).

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