Toán Lớp 8: Tìm x: a) 2x^2 -10x = 0 b) 5x(х- 2000) -х+2000=0

Question

Toán Lớp 8:  Tìm x: a) 2x^2 -10x = 0 b) 5x(х- 2000) -х+2000=0

khanhlanchau · Answer

$ text{a) Ta c&oacute;: 2}$$x^{2}-10x=0$   &rArr;$ text{2x.(x-5)=0}$   &rArr; ( left[  begin{array}{l}2x=0  x-5=0 end{array}  right. )    &rArr; ( left[  begin{array}{l}x=0  x=5 end{array}  right. )    $ text{-&Aacute;p dụng phương ph&aacute;p đặt nh&acirc;n tử chung}$   ____________________________________   $ text{B) Ta c&oacute;: 5x.(x-2000)-x+2000=0}$   &rArr;$ text{5x.(x-2000)-(x-2000)=0}$   &rArr;$ text{(5x-1).(x-2000)=0}$   &rArr; ( left[  begin{array}{l}5x-1=0  x-2000=0 end{array}  right. )    &rArr; ( left[  begin{array}{l}5x=1  x=2000 end{array}  right. )    &rArr; ( left[  begin{array}{l}x= dfrac{1}{5}  x=2000 end{array}  right. )     text{-&Aacute;p dụng phương ph&aacute;p đặt nh&acirc;n tử chung}    text{#mct}

hienthucthu97 · Answer

a) 2x^2 - 10x = 0     &hArr; 2x ( x - 5 ) = 0     &hArr; x ( x - 5 ) = 0     &hArr;  ( left[  begin{array}{l}x=0  x-5=0 end{array}  right. )      &hArr;  ( left[  begin{array}{l}x=0  x=5 end{array}  right. )      Vậy x = 0 ; x = 5     b) 5x ( x - 2000 ) - x + 2000 = 0     &hArr; 5x ( x - 2000 ) - ( x - 2000 ) = 0     &hArr; ( x - 2000 ) ( 5x - 1 ) = 0     &hArr;  ( left[  begin{array}{l}x-2000=0  5x-1=0 end{array}  right. )      &hArr;  ( left[  begin{array}{l}x=2000  x= frac{1}{5} end{array}  right. )      Vậy x = 2000 ; x = 1/5