Toán Lớp 8: (12x – 5)(4x – 1) + (3x – 7)(1 – 16x) = 81 giúp mình

Question

Toán Lớp 8:  (12x – 5)(4x – 1) + (3x – 7)(1 – 16x) = 81 giúp mình

bichquyenlien · Answer

Giải đáp + Lời giải và giải thích chi tiết:      Ta c&oacute;: $(12x &ndash; 5)(4x &ndash; 1) + (3x &ndash; 7)(1 &ndash; 16x)$     = 12x.(4x &ndash; 1) + (&ndash;5).(4x &ndash; 1) + 3x.(1 &ndash; 16x) + (&ndash;7).(1 &ndash; 16x)     = 48x^2 &ndash; 12x &ndash; 20x + 5 + 3x &ndash; 48x^2 &ndash; 7 + 112x     = (48x^2 &ndash; 48x^2) + (&ndash; 12x &ndash; 20x + 3x + 112x) + (5 &ndash; 7)     = 83x &ndash; 2     &rArr; 83x &ndash; 2 = 81          83x = 81 + 2           83x = 83             x = 83 : 83              x = 1.

kimnguenoanh · Answer

(12x &ndash; 5)(4x &ndash; 1) + (3x &ndash; 7)(1 &ndash; 16x) = 81 12x.(4x -1) + (-5).(4x -1) + 3x. (1 &ndash; 16x) + (-7).(1 &ndash; 16x) = 81 48x&sup2; -12x -20x +5 +3x -48x&sup2; -7 +112x = 81 48x&sup2; - 48x&sup2; -12x +20x +3x + 112x + 5 -7 = 81                                 83x                  - 2  = 81                                 83x                        = 81 + 2                                 83x                        = 83                                     x                        = 83 : 83                                     x                        = 1