Final answer:
The value of 2a - b is determined by expanding the left side of the given equation, comparing terms, and substituting the values into the expression. In this case, it seems there was a mismatch as the calculated answer (7) was not among the provided choices. This discrepancy suggests an error either in the question or calculations.
Step-by-step explanation:
The question asks us to determine the value of 2a - b in the equation (x-1)(x+9) = x² + ax - b. To do this, we need to expand the left side of the equation and compare it with the right side.
Expanding the left side, we get:
(x - 1)(x + 9) = x² + 9x - x - 9
= x² + 8x - 9
Now, we compare this with the equation: x² + ax - b.
We can see that a equates to 8, and b equates to 9. To find 2a - b, we substitute the values we found into the expression:
2a - b = 2(8) - 9
= 16 - 9
= 7
However, upon reviewing the available answer options, we see that 7 is not listed, indicating there may be an error in our calculations or the question itself.