（a-2)*(a-3)+2(a+3)*(a-5),其中a=3又1/2 （y-2)*(y^2-6y-9)-y(y^2-2y-15),其中y=1/2

题目

（a-2)*(a-3)+2(a+3)*(a-5),其中a=3又1/2 （y-2)*(y^2-6y-9)-y(y^2-2y-15),其中y=1/2
运用整式的乘法——多项式乘多项式 解答

答案

(a-2)(a-3)+2(a+3)(a-5)
=a^2-5a+6+2(a^2-2a-15)
=a^2-5a+6+2a^2-4a-30
=3a^2-9a-24
=3×49/4-9×7/2-24
=147/4-63/2-24
=147/4-126/4-24
=21/4-24
=-75/4
(y-2)(y^2-6y-9)-y(y^2-2y-15)
=y^3-6y^2-9y-2y^2+12y+18-y^3+2y^2+15y
=-6y^2+18y+18
=-6×1/4+18×1/2+18
=-3/2+9+18
=-3/2+27
=25.5