To simplify the expression \( (9x^2 - 6x +) - (x^2 + 4x - 39) \), we first need to clarify the first part of the expression, which seems incomplete. Assuming it was meant to be \( 9x^2 - 6x + 0 \), we rewrite the expression as follows:
\[ (9x^2 - 6x + 0) - (x^2 + 4x - 39) \]
Next, we distribute the negative sign through the second parentheses:
\[ 9x^2 - 6x + 0 - x^2 - 4x + 39 \]
Now, let's combine like terms:
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For \( x^2 \) terms: \[ 9x^2 - x^2 = (9 - 1)x^2 = 8x^2 \]
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For \( x \) terms: \[ -6x - 4x = (-6 - 4)x = -10x \]
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For the constant terms: \[ 0 + 39 = 39 \]
Putting it all together, the simplified expression is:
\[ 8x^2 - 10x + 39 \]
Thus, the final answer is:
\[ 8x^2 - 10x + 39 \]