Question

Solve -3x2 + 30x - 90 = 0.

Answer 1

Answer:
`x = 5 (- or +) i√(5)`

Proof of validity is shown below.

Answer 2

`-3x^(2)+30x-90=0 \\ \\ x^(2)-10x+30=0 \\ \\ \Delta=(-10)^(2)-4*1*30=100-20=-20 \\ \\ √(\Delta)= √(-20)=i √(20) =2i √(5) \\ \\ x_(1)= (10-2i √(5) )/(2) = 5-i √(5) \\ \\ x_(2)= (10+2i √(5) )/(2) = 5+i √(5)`