Question

已知a+b=5 ab=3 求代数式a三次方b-2a二次方吧

Answer 1

(a+b)^2=a^2+2ab+b^2=25

a^2+b^2=25-2ab=19

(a-b)^2=a^2+b^2-2ab=13

a-b=±√13

a+b=5

a=(5±√13)/2

a^3b-2a^2

=a^2(ab-2)

=a^2*1

=[(5±√13)/2]^2

=(38±10√13)/4

=(19±5√13)/2