Question

4（-2mn+2m+3n）-2（3m+5n-mn），其中m+n=3,mn=-1

Answer 1

你好，砖前级：

解：
4(-2mn+2m+3n)-2(3m+5n-mn)
=-8mn+8m+12n-6m-10n+2mn
=2m+2n-6mn
=2(m+n)-6mn
∴当m+n=3，mn=-1时，
原式=2×3-6×(-1)=6+6=12

Answer 2

4(-2mn+2m+3n)-2(3m+5n-mn)
=-8mn+8m+12n-6m-10n+2mn
=-6mn+2m+2n
=-6mn+2(m+n)
=-6*(-1)+2*3
=6+6
=12

Answer 3

4（-2mn+2m+3n）-2（3m+5n-mn）
=-8mn+8m+12n-6m-10n+2mn
=-6mn+2m+2n
=-6(-1)+2(m+n)
=6+6=12

Answer 4

4（-2mn+2m+3n）-2（3m+5n-mn）
=-8mn+8m+12n-6m-10n+2mn
=-6mn+2m+2n
=-6mn+2(m+n)
=-6×(-1)+2×3
=12