Toán Lớp 8: 1, Tìm x, biết: a, (x-5).(2x+3)-2x(x-3)-(x+4)=10 b, (4x-3).(9x+1)-(12x-1).(3x+2)=20 CTLHN LUÔNN@@!!!

Question

Toán Lớp 8:  1, Tìm x, biết: a, (x-5).(2x+3)-2x(x-3)-(x+4)=10 b, (4x-3).(9x+1)-(12x-1).(3x+2)=20 CTLHN LUÔNN@@!!!

giangnguyen33 · Answer

Giải đáp+Lời giải và giải thích chi tiết:    a)   (x-5)(2x+3)-2x(x-3)-(x+4)=10   &hArr;(2x^2+3x-10x-15)-2x^2+6x-x-4=10   &hArr;2x^2-7x-15-2x^2+5x-4=10   &hArr;-2x-19=10   &hArr;-2x=29   &hArr;x=-29/2   Vậy x=-29/2   b)   (4x-3)(9x+1)-(12x-1)(3x+2)=20   &hArr;(36x^2+4x-27x-3)-(36x^2+24x-3x-2)=20   &hArr;(36x^2-23x-3)-(36x^2+21x-2)=20   &hArr;36x^2-23x-3-36x^2-21x+2=20   &hArr;-44x-1=20   &hArr;-44x=21   &hArr;x=-21/44   Vậy x=-21/44

diemchau · Answer

1. a, (x-5).(2x+3)-2x(x-3)-(x+4)=10 <=>2x^2+3x-10x-15-2x^2+6x-x-4=10 <=>-2x=10+15+4 <=>-2x=29 <=>x=-29/2 Vậy x=-29/2. b, (4x-3).(9x+1)-(12x-1).(3x+2)=20 <=>36x^2+4x-27x-3-36x^2-24x+3x+2=20 <=>-44x=20+3-2 <=>-44x=21 <=>x=-21/44 Vậy x=-21/44.