Toán Lớp 8: Thực hiện phép tính: (x+3) ² = (x-4)(x+4)= (1/2x +1) ³= (x-3/4) ²= (3x+1/2)(1/3-3x)= (x-2/3y)(x ²+2/3xy+4/9y ²)=

Question

Toán Lớp 8:  Thực hiện phép tính:  (x+3) ² =  (x-4)(x+4)=  (1/2x +1) ³=  (x-3/4) ²=  (3x+1/2)(1/3-3x)=  (x-2/3y)(x ²+2/3xy+4/9y ²)=

lanhuongthu · Answer

(x+3) &sup2; = x&sup2;+ 2.x.3 +3&sup2;= x&sup2; + 6x + 9       (x-4)(x+4)= x&sup2; - 4&sup2; = x&sup2;- 16       (1/2x +1) &sup3;= ( 1/2 x)&sup3; + 3. (1/2 x)&sup2;.1 + 3.1/2x .1&sup2; +1       1/8 x&sup3; + 3/4 x&sup2; + 3/2 x +1        (x-3/4) &sup2;= x&sup2; - 2.x .3/4 + ( 3/4) &sup2;= x&sup2; - 3/2 x + 9/16        (x-2/3y)(x &sup2;+2/3xy+4/9y &sup2;)= x&sup3; -( 2/3y)&sup3;= x - 8/27 y&sup3;

quynhthanhnhu · Answer

Giải đáp + Lời giải và giải thích chi tiết:   a) (x + 3)^2   = x^2 + 2.x.3 + 3^2   = x^2 + 6x + 9   b) (x - 4)(x + 4)   = x^2 - 4^2 = x^2 - 16   c) (1/2 x + 1)^3   = (1/2 x)^3 + 3. (1/2 x)^2 . 1 + 3 . 1/2 x . 1^2 + 1^3   = 1/8x^3 + 3/4 x^2 + 3/2 x + 1   d) (x - 3/4)^2   = x^2 - 2.x.3/4 + (3/4)^2   = x^2 - 3/2 x + 9/16   e) (3x + 1/2)(1/3 - 3x)   = x - 9x^2 + 1/6 - 3/2 x   = -9x^2 - 1/2 x + 1/6   f) ( x - 2/3 y)(x^2 + 2/3 xy + 4/9 y^2)   = x^3 - (2/3 y)^3   = x^3 - 8/27 y^3   #SunHee