Toán Lớp 8: a) 3x( x+1)- 2x (x+2)= -1-x b) 4x( x-2021)- x+2021= 0

Question

Toán Lớp 8:  a) 3x( x+1)- 2x (x+2)= -1-x b) 4x( x-2021)- x+2021= 0

annhocbichchaubich · Answer

a)   3x.(x+1)-2x.(x+2)=-1-x   =>3x.x+3x.1-2x.x-2x.2=-1-x   =>3x^2+3x-2x^2-4x=-1-x   =>(3x^2-2x^2)+(3x-4x)=-1-x   =>x^2-x=-1-x   =>x^2-x+x+1=0   =>x^2+1=0   =>x^2=-1   => Kh&ocirc;ng c&oacute; gi&aacute; trị x   $  $   b)   4x.(x-2021)-x+2021=0   =>4x.(x-2021)-(x-2021)=0   =>(x-2021).(4x-1)=0   => ( left[  begin{array}{l}x-2021=0  4x-1=0 end{array}  right. )    => ( left[  begin{array}{l}x=2021  4x=1 end{array}  right. )    => ( left[  begin{array}{l}x=2021  x= dfrac{1}{4} end{array}  right. )    Vậy x=2021; x= frac{1}{4}

doanthulan · Answer

Giải đáp+Lời giải và giải thích chi tiết:    a)   3x(x + 1) - 2x(x + 2) = - 1 - x   3x^2 + 3x - 2x^2 - 4x - ( - 1 - x) = 0   3x^2 + 3x - 2x^2 - 4x + 1+ x = 0   (3x^2 - 2x^2) - (4x - 3x - x) + 1 = 0   x^2 + 1 = 0   V&igrave; x^2 >= 0 AA x   => x^2 + 1 >= 1 > 0 AA x   => Kh&ocirc;ng c&oacute; gi&aacute; trị x thỏa m&atilde;n đề b&agrave;i.   b)   4x(x - 2021) - x + 2021 = 0   4x(x - 2021) - (x - 2021)1 = 0   (x - 2021)(4x - 1) = 0   => x - 2021 = 0 hoặc 4x - 1 = 0   => x = 2021 hoặc x = 1/4   Vậy x = 2021 hoặc x = 1/4   #SunHee