Môn Toán Lớp 8: KHAI TRỂN VÀ RÚT GỌN: a) ( 3-2x) mũ 2 b) ( 3x-2) * ( 3x+2) c) ( a+2) mũ 2- (a+2) * (a-2) d)( 3x+ 4)mũ 2-10x – (x-4) * (x=+4)

Trả Lời

1. a) (3-2x)^2

   = 3^2 – 2*3*2x + (2x)^2

   = 9 – 12x + 4x^2

   b) (3x-2)(3x+2)

   = (3x)^2 – 2^2

   = 9x^2 – 4

   c) (a+2)^2-(a+2)(a-2)

   = a^2+2ab+b^2-(a^2-2^2)

   = a^2+2ab+b^2-a^2+4

   = 2ab + b^2 + 4

   d) (3x+4)^2-10x-(x-4)(x+4)

   = 9x^2+24x+16-10x-(x^2-4^2)

   = 9x^2+24x+16-10x-x^2+16

   = 8x^2 + 14x + 36

   Trả lời
2. a) (3-2x)^2

   =3^2-2*3*2x+(2x)^2

   =9-12x+4x^2

   b) (3x-2)(3x+2)

   =(3x)^2-2^2

   =9x^2-4

   c) (a+2)^2-(a+2)(a-2)

   =a^2+2*a*2+2^2-(a^2-2^2)

   =a^2+4a+4-a^2+4

   =4a+8

   d) (3x+4)^2-10x-(x-4)(x+4)

   =(3x)^2+2*3x*4+4^2-10x-(x^2-4^2)

   =9x^2+24x+16-10x-x^2+16

   =8x^2+14x+32

   Trả lời