Which equation shows the quadratic formula used correctly to solve 7 x squared is equal to 9 plus x for x ?

Rewrite the equation in standard form: 7x² − x − 9 = 0, so a = 7, b = −1, and c = −9. Substituting into the quadratic formula gives x = (1 ± √(1 − 4·7·(−9)))/(2·7) = (1 ± √(1 + 4·7·9))/14. This matches choice C, with numerator 1 plus or minus the square root of (−1)² + 4·7·9.

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