Toán Lớp 8: Tính ( rút gọn) (1+3x)(3x-1) (2x-3)^2+(3x-3)^2 (2x-1)^2-(x-2)(x+2) (3x+2)(3x-3)-(4x-3)^2

Question

Toán Lớp 8:  Tính ( rút gọn)   (1+3x)(3x-1) (2x-3)^2+(3x-3)^2 (2x-1)^2-(x-2)(x+2) (3x+2)(3x-3)-(4x-3)^2

cobexinhdep · Answer

a) (1+3x)(3x-1)      = 3x-1+9x&sup2;-3x                                 =9x&sup2;-1                                  =(3x-1)(3x+1)       b)(2x-3)&sup2;+ (3x-3)&sup2;=4x&sup2;-12x +9 +9x&sup2;-18x +9                                      =13x&sup2;-30x+18       c) (2x-1)&sup2;-(x-2)(x+2)=4x&sup2;-4x+1 -(x&sup2;-4)                                          =4x&sup2;-4x+1-x&sup2;+4                                          =3x&sup2;-4x +5       d)(3x+2)(3x-3)-(4x-3)&sup2;=9x&sup2;-9x+6x-6 -(16x&sup2;-24x+9)                                              = 9x&sup2;-9x+6x-6-16x&sup2;+24x-9                                              =-7x&sup2;+21x-15

buithaianh98 · Answer

Giải đáp + Lời giải và giải thích chi tiết:   (1+3x)(3x-1)   Ta c&oacute; : (a+b)(a-b) = a^2 - b^2   = (3x)^2 - 1^2   = 9x^2 - 1   (2x-3)^2 + (3x-3)^2   = 4x^2 - 12x + 9 + 9x^2 - 18x + 9   = (4x^2+9x^2) - (12x+18x) + (9+9)   = 13x^2 - 30x + 18   (2x-1)^2-(x-2)(x+2)   = 4x^2 - 4x + 1 - x^2 + 4   = (4x^2-x^2) - 4x + (4+1)   = 3x^2 - 4x + 5   (3x+2)(3x-3)-(4x-3)^2   = 9x^2 - 3x - 6 - 16x^2 + 24x - 9   = (9x^2-16x^2) + (24x-3x) - (6+9)   = -7x^2 + 21x - 15