How do you solve $x^{2} - x - 72 = 0$ $x^2-x-72=0$ ?

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Answer 1 · 2017-03-14T12:02:50

$x = 9 or x = - 8$ $x=9" "or x=-8$ are the two solutions.

To solve a quadratic equation (one with an $x^{2}$ $x^2$ term), there are three options:

In this case the quadratic trinomial can be factored.

$x^{2} - x - 72 = 0$ $x^2 -x-72 =0" "$ find factors of 72 which differ by 1.

$(x - 9) (x + 8) = 0$ $(x-9)(x+8)=0$

Either of the factors could be equal to $0$ $0$ .

If $x - 9 = 0 \Leftrightarrow x = 9$ $x-9=0" "hArr" " x =9$

If $x + 8 = 0 \Leftrightarrow x = - 8$ $x+8=0" "hArr" "x =-8$

$x = 9 or x = - 8$ $x=9" "or x=-8$ are the two solutions.

How do you solve x^2-x-72=0x2−x−72=0x^2-x-72=0?