Question

若m+n=3,求代数式2m的平方+4mn+2n的平方-6的值

Answer 1

2m*+4mn+2n*-6=2(m*+2mn+n*)-6=2(m+n)*-6=2x3*-6=12*=2 （平方的意思）

Answer 2

2m^2+4mn+2n^2-6
=2(m^2+2mn+n^2)-6
=2(m+n)^2-6
=2*3^2-6
=18-6
=12

Answer 3

12