Toán Lớp 8: Giải hộ tui nhen a). (x+2)(x-3)-(x-2)(x+5)=6 b). (3x-2)(2x+9)-(x+2)(6x+1)=(x+1)-(x-6)

Question

Toán Lớp 8:  Giải hộ tui nhen  a). (x+2)(x-3)-(x-2)(x+5)=6 b). (3x-2)(2x+9)-(x+2)(6x+1)=(x+1)-(x-6)

minhhaanh · Answer

a)  (x+2)(x-3) - (x-2)(x+5) = 6     => x&sup2; + 3x + 2x + 6 - ( x&sup2; + 5x - 2x - 10 ) = 6     => x&sup2; + 5x + 6 - x&sup2; - 3x + 10 = 6     => 2x + 16 = 6     => 2x          = -10     =>   x          = -10 : 2     =>   x          = -5     b) (3x-2)(2x+9) - (x+2)(6x+1) = (x+1) - (x-6)     => 6x&sup2; + 27x + 4x + 18 - ( 6x&sup2; + x + 12x + 2 ) = x + 1 - x + 6     => 6x&sup2; + 31x + 18 - 6x&sup2; - 13x - 2 = 7     => 18x + 16 = 7     => 18x          = 7 - 16     => 18x          = -9     => x              = -1/2

haianhtu97 · Answer

Ta c&oacute;:  (x+2)(x-3)-(x-2)(x+5)=6       &rArr;x&sup2;-3x+2x-6-(x&sup2;+5x-2x-10)=6       &rArr;x&sup2;-x-6-x&sup2;-5x+2x+10=6       &rArr;x&sup2;-x-6-x&sup2;-3x+10=6       &rArr;-4x+4=6       &rArr;-4x=2       &rArr;x=-1/2       b,Ta c&oacute;: (3x-2)(2x+9)-(x+2)(6x+1)=(x+1)-(x-6)       &rArr;6x&sup2;+27x+4x+18-6x&sup2;-x-12x-2=x+1-x+6       &rArr;18x+16=7       &rArr;18x=-9       &rArr;x=-1/2      Xin hay nhất