Toán Lớp 8: b1 1) x.(a-b) + a-b 2) m.(x+y)+x+y 3)x.(a+b)-a-b 4)ax+ay-2x-2y 5)a² -4b² 6)(a+b)² -4 b2 tìm x 1) x² -7x=0 2)x² +3x-2x-6=0 3) x²

Question

Toán Lớp 8:  b1  1) x.(a-b) + a-b 2) m.(x+y)+x+y  3)x.(a+b)-a-b 4)ax+ay-2x-2y  5)a² -4b²  6)(a+b)² -4   b2 tìm x  1) x² -7x=0 2)x² +3x-2x-6=0 3) x² -81=0

khanhlanchau · Answer

Đáp án nha

hienthucthu97 · Answer

B1.       1)       x.(a-b) + a-b        =(a-b)(x+1)         2)        m.(x+y)+x+y        =(x+y)(m+1)         3)         x.(a+b)-a-b         =x.(a+b)-(a+b)        =(a+b)(x-1)       4)       ax+ay-2x-2y        =a(x+y) -2(x+y)         =(x+y)(a-2)         5)         a&sup2;-4b&sup2;         =a&sup2;-(2b)&sup2;         =(a-2b)(a+2b)         6)         (a+b)&sup2;-4         =(a+b)&sup2;-2&sup2;         =(a+b+2)(a+b-2)         B2.         1)             x&sup2; -7x=0         &hArr;x(x-7)=0         &hArr; $ left[ begin{matrix} x=0   x-7=0 end{matrix} right.$         &hArr; $ left[ begin{matrix} x=0   x=7 end{matrix} right.$         &rArr;S={0;7}         2)         x&sup2; +3x-2x-6=0         &hArr;x(x +3) - 2(x+3)=0         &hArr;(x+3)(x-2)=0         &hArr;$ left[ begin{matrix} x+3=0   x-2=0 end{matrix} right.$         &hArr; $ left[ begin{matrix} x=-3   x=2 end{matrix} right.$         &rArr;S={-3;2}         3)         x&sup2; -81=0         &hArr;x&sup2;-9&sup2;=0         &hArr;(x-9)(x+9)=0         &hArr;$ left[ begin{matrix} x-9=0   x+9=0 end{matrix} right.$         &hArr; $ left[ begin{matrix} x=9   x=-9 end{matrix} right.$         &rArr;S={-9;9}