Question

Use the quadratic formula to find the zeros of the function. Round to the nearest tenth if necessary
x^2+5x-84=0

{-12, 7}

{7, 12}

{-7, 12}

No Real Solution

Answer 1

first one

Answer 2

\[\Delta = b ^{2} -4ac = 25 - 4 (1)(-84)= 361\]
\[x = (- b \pm \sqrt{\Delta}) / 2a = (-5 \pm \sqrt{61})/2(1) = (-5 \pm 19)/2(1)\]
X= 7 or -12

Answer 3

Or you could simply do like this:
\[x ^{2} + 5x - 84 = x ^{2} - 7x + 12x - 84 = x(x-7) + 12(x-7) = (x-7)(x+12)\]
Thus, x = 7 or -12