Toán Lớp 8: Tìm x a) 4(x-1)-x^2(x-1)=0 b) 5x(x-2)-3x^2=2(x-5)^2 Gấp lắm ạ

Question

Toán Lớp 8:  Tìm x a) 4(x-1)-x^2(x-1)=0 b) 5x(x-2)-3x^2=2(x-5)^2 Gấp lắm ạ

tuyen98 · Answer

a. 4(x-1)-x^2(x-1)=0   -> (x-1)x(4-x^2)=0   -> x-1=0 hoặc 4-x^2=0   -> x=1 hoặc x=2,x=-2   Vậy x1=-2 , x2=1 , x3=2   b. 5x(x-2)-3x^2=2(x-5)^2   -> 5x^2-10x-3x^2=2(x-5)^2   -> 5x^2-10x-3x^2=2(x^2-10x+25)   -> 2x^2-10x=2(x^2-10x+25)   -> 2x^2-10x=2x^2-20x+50   -> -10x=-20x+50   -> -10x+20x=50   -> 10x=50   -> x=5   Vậy x=5

hoaiphuong85 · Answer

a) 4 (x-1) - x&sup2;(x-1) = 0   &hArr; (x-1)(4 - x&sup2;) = 0   &hArr; (x-1)(2&sup2; - x&sup2;) = 0   &hArr; (x-1)(2-x)(2+x) = 0   &hArr;  ( left[  begin{array}{l}x=&plusmn;2  x=1 end{array}  right. )     Vậy x = 1 ; x=2; x=-2      b) 5x(x-2) -3x&sup2; = 2(x-5)&sup2;   &hArr; 5x&sup2; - 10x - 3x&sup2; = 2 (x&sup2; - 10x +25)   &hArr; 2x&sup2; -10x = 2x&sup2; -20x +50   &hArr; (2x&sup2; - 2x&sup2; ) + ( -10x +20x) = 50   &hArr; 10x =50   &hArr; x= 5   Vậy x=5