Question

已知a^2+ab=4,ab+b^2=-1，求a^2+3ab+2b^2 要有过程

Answer 1

a^2+3ab+2b^2 =(a^2+ab)+2(ab+b^2)=4+2×（-1）=4-2=2

Answer 2

a^2+3ab+2b^2=a^2+ab+2*（ab+b^2）=4+2*（-1）=2

Answer 3

a^2+3ab+2b^2

=（a^2+ab)+2X(ab+b^2)
=4-2
=2