bài tập toán

Question

Thực hiện các phép tính sau:

a) 15x7y3.2y2x215x7y3.2y2x2;           b) 4y211x4.(−3x28y)4y211x4.(−3x28y);           c) x3−85x+20.x2+4xx2+2x+4

Answer 1

a) 15x7y3.2y2x215x7y3.2y2x2 =15x.2y27y3x2=30xy27x2y3=307xy=15x.2y27y3x2=30xy27x2y3=307xy

b) 4y211x4.(−3x28y)4y211x4.(−3x28y) =−4y2.3x211x4.8y=−3x2y211.2x4y=−3y22x2=−4y2.3x211x4.8y=−3x2y211.2x4y=−3y22x2

c) x3−85x+20.x2+4xx2+2x+4x3−85x+20.x2+4xx2+2x+4 

    =(x3−8)(x2+4x)5(x+4)(x2+2x+4)=(x3−8)(x2+4x)5(x+4)(x2+2x+4)

    =x(x−2)(x2+2x+4)(x+4)5(x+4)(x2+2x+4)=x(x−2)5