Step-by-step explanation:
so, it is a quadratic equation :
-3x² + 30x - 90 = 0
the first thing we can do is divide by 3
-x² + 10x - 30 = 0
remember, the formula to solve and find the 2 solutions is
x = (-b ± sqrt(b² - 4ac))/(2a)
in our case here
a = -1
b = 10
c = -30
x = (-10 ± sqrt(100 - 4×-1×-30))/-2 =
= (-10 ± sqrt(100 - 120))/-2 = (-10 ± sqrt(-20))/-2 =
= (-10 ± sqrt(4×5)i)/-2 = (-10 ± 2×sqrt(5)i)/-2 =
= 5 ± -sqrt(5)i
x1 = 5 - sqrt(5)i
x2 = 5 + sqrt(5)i
remember, i = sqrt(-1), a complex number.
