Question

若a平方加b平方等于六则代数式括号三a平方减去二ab减去b平方括回来减去括号a

Answer 1

a^2+b^2=6

(3a^2-2ab-b^2)-(a^2-2ab-3b^2)

=3a^2-2ab-b^2-a^2+2ab+3b^2

=2a^2+2b^2

=2(a^2+b^2)

=2*6

=12