помогите решить плиз Х*Х+Х-72=0

Х*Х+Х-72=0

x^2 + x - 72 = 0

D = b^2-4ac = 1^2 - 4*1*(-72) = 1+288 = 289

VD = V289 = 17

            -1+17             16

x1 = ------------- = ------------ = 8

                2                   2

            -1-17            -18

x2 = -------------- = ----------- = -9

                2                  2

ответ: х=-9 i х = 8