Question

If the product of two of the roots x^4-8x^3+21x^2-20x+5=0 is 5 then the roots are​

Answer 1

x4−8x3+21x2−20x+5=(x2−4x+a)(x2−4x+b)

⎧⎩⎨a+b+16=21−4a−4b=−20ab=5

So a+b=5 and ab=5.

a, b are the roots of t2−5t+5=0.