Toán Lớp 8: Tìm x biết: a/ 3x( 2x +7) – ( x+ 1)( 6x -5) = 10 b/ (x – 4)² – 36 =0 c/3(2x – 1) – 5( x – 3) =4

Question

Toán Lớp 8:  Tìm x biết: a/ 3x( 2x +7) – ( x+ 1)( 6x -5) = 10                b/ (x – 4)² – 36 =0 c/3(2x – 1) – 5( x – 3) =4                              d/ (2x – 1)2 – (x+3)2 = 0 e/ (x – 3)(x – 7) – x2  = 1                              f/ ( x +2)² – ( x – 2)( x-1) = 0 g/ ( x – 1)²– ( x – 2)( x+2)  = 0                      h/ ( 10x + 9).x – ( 5x – 1)(2x +3) = 8

truongthanhhung · Answer

……?.?

kimoanh34 · Answer

Giải đáp+Lời giải và giải thích chi tiết:    a) 3x(2x + 7) - (x + 1)(6x - 5) = 10   &hArr; 6x&sup2; + 21x - 6x&sup2; + 5x - 6x + 5 = 10   &hArr; 20x = 5   &hArr;   x =  frac{1}{4}   b) (x - 4)&sup2;- 36 = 0   &hArr; (x - 4 - 6)(x - 4 + 6) = 0   &hArr; (x - 10)(x + 2) = 0   &rArr; x = 10   hoặc x = - 2   c) 3(2x - 1) - 5(x - 3) = 4   &hArr; 6x - 3 - 5x + 15 = 4   &hArr; x = 4 - 15 + 3   &hArr; x = - 8   d) (2x - 1)&sup2; - (x + 3)&sup2; = 0   &hArr; (2x - 1 - x - 3)(2x - 1 + x + 3) = 0   &hArr; (x - 4)(3x + 2) = 0   &rArr; x = 4   hoặc x =  frac{-2}{3}   e) (x - 3)(x - 7) - x&sup2; = 1   &hArr; x&sup2; - 7x - 3x + 21 - x&sup2; = 1   &hArr; - 10x = - 20   &hArr;   x = 2   f) (x + 2)&sup2; - (x - 2)(x - 1) = 0   &hArr; x&sup2; + 4x + 4 - x&sup2; + x + 2x - 2 = 0   &hArr; 7x + 2 = 0   &hArr; x =  frac{-2}{7}   g) (x - 1)&sup2; - (x + 2)(x - 2) = 0   &hArr; x&sup2; - 2x + 1 - x&sup2; + 4 = 0   &hArr; - 2x + 5 = 0   &hArr;  x =  frac{5}{2}   h) (10x + 9)x - (5x - 1)(2x + 3) = 8   &hArr; 10x&sup2; + 9x - 10x&sup2; - 15x + 2x + 3 = 8   &hArr; - 4x = 5   &hArr; x =  frac{-5}{4}