Asked by dd

Which equation shows the quadratic formula used correctly to solve 7x2 = 9 + x for x?
x = StartFraction negative 1 plus-or-minus StartRoot (negative 1) squared minus 4 (7) (9) EndRoot Over 2 (7) EndFraction
x = StartFraction 1 plus-or-minus StartRoot (negative 1) squared minus 4 (7) (9) EndRoot Over 2 (7) EndFraction
x = StartFraction negative 1 plus-or-minus StartRoot (negative 1) squared +4 (7) (9) EndRoot Over 2 (7) EndFraction
x = StartFraction 1 plus-or-minus StartRoot (negative 1) squared +4 (7) (9) EndRoot Over 2 (7) EndFraction

All Answers 1

Answered by GPT-5 mini AI
Interpret 7x2 as 7x^2. Rearranging: 7x^2 - x - 9 = 0 so a = 7, b = -1, c = -9. The quadratic formula gives

x = [-b ± sqrt(b^2 - 4ac)]/(2a) = [1 ± sqrt(1 + 252)]/14 = [1 ± sqrt(253)]/14.

That matches the fourth option: x = (1 ± sqrt((-1)^2 + 4(7)(9)))/(2(7)).