Toán Lớp 8: Rút gọn biểu thức: a) P= (2x-1) 4x^2+ 2x+1+ (x+1) x^2- x+1 b) Q= (x-y) x^2+ xy+y^2- (x+y) x^2- xy+y^2+ 2y^3

Question

Toán Lớp 8:  Rút gọn biểu thức:  a) P= (2x-1) 4x^2+ 2x+1+ (x+1) x^2- x+1  b) Q= (x-y) x^2+ xy+y^2- (x+y) x^2- xy+y^2+ 2y^3

thanhthuythu · Answer

a) P= (2x-1) 4x^2+ 2x+1+ (x+1) x^2- x+1     =8x^3-4x^2+2x+1+x^3+x^2-x+1     =9x^3-3x^2+x+2         b) Q= (x-y) x^2+ xy+y^2- (x+y) x^2- xy+y^2+ 2y^3     =x^3-x^2y+xy+y^2-x^3-x^2y-xy+y^2+2y^3     =2y^2-2x^2y+2y^3

behocgioitoan · Answer

Giải đáp:   a)P=9x&sup3;-3x&sup2;+x+2   b)Q=-2x&sup2;y+2y&sup2;+2y&sup3;   Lời giải và giải thích chi tiết:   a)P=(2x-1)4x&sup2;+2x+1+(x+1)x&sup2;-x+1          =8x&sup3;-4x&sup2;+2x+1+x&sup3;+x&sup2;-x+1          =(8x&sup3;+x&sup3;)+(-4x&sup2;+x&sup2;)+(2x-x)+(1+1)          =9x&sup3;-3x&sup2;+x+2   b)Q=(x-y)x&sup2;+xy+y&sup2;-(x+y)x&sup2;-xy+y&sup2;+2y&sup3;           =x&sup3;-x&sup2;y+xy+y&sup2;-x&sup3;-x&sup2;y-xy+y&sup2;+2y&sup3;           =(x&sup3;-x&sup3;)+(-x&sup2;y-x&sup2;y)+(xy-xy)+(y&sup2;+y&sup2;)+2y&sup3;           =-2x&sup2;y+2y&sup2;+2y&sup3;