Toán Lớp 8: Giải các phương trình sau: a, (x – 1)(5x + 3) = (3x – 8)(x – 1) b, 3x(25x + 15) – 35(5x + 3) = 0 c, (2 – 3x)(x + 11) = (3x – 2)(2 – 5x)

Question

Toán Lớp 8:  Giải các phương trình sau: a, (x – 1)(5x + 3) = (3x – 8)(x – 1) b, 3x(25x + 15) – 35(5x + 3) = 0 c, (2 – 3x)(x + 11) = (3x – 2)(2 – 5x) d, (2x2 + 1)(4x – 3) = (2x2 + 1)(x – 12) e, (2x – 1)2 + (2 – x)(2x – 1) = 0 f, (x + 2)(3 – 4x) = x2 + 4x + 4

thienthanh · Answer

Đây nhé

buithaianh98 · Answer

@Min         Giải đáp+Lời giải và giải thích chi tiết:      a, (x &ndash; 1)(5x + 3) = (3x &ndash; 8)(x &ndash; 1)   &hArr; (x &ndash; 1)(5x + 3) &ndash; (3x &ndash; 8)(x &ndash; 1) = 0   &hArr; (x &ndash; 1)[(5x + 3) &ndash; (3x &ndash; 8)] = 0   &hArr; (x &ndash; 1)(5x + 3 &ndash; 3x + 8) = 0   &hArr; (x &ndash; 1)(2x + 11) = 0 &hArr; x &ndash; 1 = 0 hoặc 2x + 11 = 0   x &ndash; 1 = 0 &hArr; x = 1   2x + 11 = 0 &hArr; x = -5,5   Vậy phương tr&igrave;nh c&oacute; nghiệm x = 1 hoặc x = -5,5   b, 3x(25x + 15) &ndash; 35(5x + 3) = 0   &hArr; 15x(5x + 3) &ndash; 35(5x + 3) = 0   &hArr; (15x &ndash; 35)(5x + 3) = 0 &hArr; 15x &ndash; 35 = 0 hoặc 5x + 3 = 0   15x &ndash; 35 = 0 &hArr; x = 35/15 = 7/3   5x + 3 = 0 &hArr; x = - 3/5   Vậy phương tr&igrave;nh c&oacute; nghiệm x = 7/3 hoặc x = -3/5   c, (2 &ndash; 3x)(x + 11) = (3x &ndash; 2)(2 &ndash; 5x)   &hArr; (2 &ndash; 3x)(x + 11) &ndash; (3x &ndash; 2)(2 &ndash; 5x) = 0   &hArr; (2 &ndash; 3x)(x + 11) + (2 &ndash; 3x)(2 &ndash; 5x) = 0   &hArr; (2 &ndash; 3x)[(x + 11) + (2 &ndash; 5x)] = 0   &hArr; (2 &ndash; 3x)(x + 11 + 2 &ndash; 5x) = 0   &hArr; (2 &ndash; 3x)(13 &ndash; 4x) = 0 &hArr; 2 &ndash; 3x = 0 hoặc 13 &ndash; 4x = 0   2 &ndash; 3x = 0 &hArr; x = 2/3   13 &ndash; 4x = 0 &hArr; x = 13/4   Vậy phương tr&igrave;nh c&oacute; nghiệm x = 2/3 hoặc x = 13/4   d, (2x 2    + 1)(4x &ndash; 3) = (2x2 + 1)(x &ndash; 12)   &hArr; (2x 2    + 1)(4x &ndash; 3) &ndash; (2x2 + 1)(x &ndash; 12) = 0   &hArr; (2x 2    + 1)[(4x &ndash; 3) &ndash; (x &ndash; 12)] = 0   &hArr; (2x 2    + 1)(4x &ndash; 3 &ndash; x + 12) = 0   &hArr; (2x 2    + 1)(3x + 9) = 0 &hArr; 2x 2    + 1 = 0 hoặc 3x + 9 = 0   2x2 + 1 = 0: v&ocirc; nghiệm (v&igrave; 2x2 &ge; 0 n&ecirc;n 2x2 + 1 > 0)   3x + 9 = 0 &hArr; x = - 3   Vậy phương tr&igrave;nh c&oacute; nghiệm x = -3   e, (2x &ndash; 1)2 + (2 &ndash; x)(2x &ndash; 1) = 0   &hArr; (2x &ndash; 1)(2x &ndash; 1) + (2 &ndash; x)(2x &ndash; 1) = 0   &hArr; (2x &ndash; 1)[(2x &ndash; 1) + (2 &ndash; x)] = 0   &hArr; (2x &ndash; 1)(2x &ndash; 1 + 2 &ndash; x) = 0   &hArr; (2x &ndash; 1)(x + 1) = 0 &hArr; 2x &ndash; 1 = 0 hoặc x + 1 = 0   2x &ndash; 1 = 0 &hArr; x = 0,5   x + 1 = 0 &hArr; x = - 1   Vậy phương tr&igrave;nh c&oacute; nghiệm x = 0,5 hoặc x = - 1   f, (x + 2)(3 &ndash; 4x) = x2 + 4x + 4   &hArr; (x + 2)(3 &ndash; 4x) &ndash; (x + 2)2 = 0   &hArr; (x + 2)(3 &ndash; 4x) &ndash; (x + 2)(x + 2) = 0   &hArr; (x + 2)[(3 &ndash; 4x) &ndash; (x + 2)] = 0   &hArr; (x + 2)(3 &ndash; 4x &ndash; x &ndash; 2) = 0   &hArr; (x + 2)(1 &ndash; 5x) = 0 &hArr; x + 2 = 0 hoặc 1 &ndash; 5x = 0   x + 2 = 0 &hArr; x = - 2   1 &ndash; 5x = 0 &hArr; x = 0,2   Vậy phương tr&igrave;nh c&oacute; nghiệm x = - 2 hoặc x = 0,2