Answer:
4x4-7x2-36 = 0
are either :
x =√ 4.000 = 2.00000 or :
x =√ 4.000 = -2.00000 or :
x =√-2.250 = 0.0 + 1.50000 i or :
x =√-2.250 = 0.0 - 1.50000 i
Hope it helped
