If #alpha,beta# are the roots of equation #x^2-px+q=0# then find the quadratic equation the roots of which are #(alpha^2-beta^2)(alpha^3-beta^3) & alpha^3 beta^2+ alpha^2 beta^3#?
2 Answers
Explanation:
Given:
#x^2-px+q = (x-alpha)(x-beta) = x^2-(alpha+beta)x+alphabeta#
We have:
#{ (alpha+beta = p), (alphabeta = q) :}#
Hence:
#(alpha^2-beta^2)(alpha^3-beta^3) = (alpha-beta)^2(alpha+beta)(alpha^2+alphabeta+beta^2)#
#color(white)((alpha^2-beta^2)(alpha^3-beta^3)) = (alpha^2-2alphabeta+beta^2)(alpha+beta)(alpha^2+alphabeta+beta^2)#
#color(white)((alpha^2-beta^2)(alpha^3-beta^3)) = ((alpha+beta)^2-4alphabeta)(alpha+beta)((alpha+beta)^2-alphabeta)#
#color(white)((alpha^2-beta^2)(alpha^3-beta^3)) = (p^2-4q)p(p^2-q)#
#color(white)((alpha^2-beta^2)(alpha^3-beta^3)) = p^5-5p^3q+4pq^2#
and:
#alpha^3beta^2+alpha^2beta^3 = (alpha+beta)(alphabeta)^2 = pq^2#
So the monic quadratic equation with the these two roots can be written:
#0 = x^2-((p^5-5p^3q+4pq^2) + pq^2)x + (p^5-5p^3q+4pq^2)pq^2#
#color(white)(0) = x^2-(p^5-5p^3q+5pq^2)x + (p^6q^2-5p^4q^3+4p^2q^4)#
Equation is
Explanation:
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The quadratic equation whose roots are given is
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Sum of roots is
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and product of roots is
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Hence equation is