Question

已知a+b=1,ab=-2,求代数式(-2ab+10a+3b)-3(ab-a-2b)+2(a+3b+ab)的值

Answer 1

把a+b=1,ab=-2 代入

(-2ab+10a+3b)-3(ab-a-2b)+2(a+3b+ab)

=（-2*-2+10a+3b)-3*(-2-a-2b)+2(a+3b-2)

= 4+10a+3b+3a+2b-6+2a+6b-4

= 15a+11b-6

= 26 * -2 - 6

= - 19