- #1
Maatttt0
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Homework Statement
The quadratric equation x^2 - 5x + 7 = 0 has the roots α and β. Find the quadratic equation with roots α^3 and β^3.
Homework Equations
N/a
The Attempt at a Solution
u = α^3
α = u^(1/3)
u^(2/3) - 5(1/3) + 7 = 0
u^(1/3)[u - 5] = -7 --- minus 7 off each side followed by taking cubic root u out of the left side.
u[u - 5] = -343 --- put everything to the power of 3.
u^2 - 5u + 343 = 0
but the answer is u^2 – 20u + 343 = 0
I cannot see where I've gone wrong - help me please :) thank you