Question

I need to find all roots of x^4 - 64x

Answer 1

Hello from MrBillDoesMath!

Answer:    0, 4,  -2 -2 sqrt(3) i,  -2 + 2 sqrt(3) i

Discussion:

Factor the expression:

x^4 - 64x   = x (x^3 -64)   =  x (x-4)* (x^2 +4x + 16)    

The roots  0, 4 are evident from the above factorization. Use the quadratic formula to find the roots of the quadratic. They are

x = -2 -2 sqrt(3) i

x = -2 + 2 sqrt(3) i

Thank you,

MrB