Lời giải :
a, Sửa đề thành `x^2 + 2x ``x^2+2x``=x(x+2)`b, `( 3-2x )( 5-x ) - 2( x-5 )^2``=(3-2x)(5-x)-2(5-x)^2``=(5-x)[3-2x-2(5-x)]``=(5-x)(3-2x-10+2x)``=-7(5-x)`c, `( 2x -1 )^2 - ( 3-x )( 1-2x )``=(2x-1)^2+(3-x)(2x-1)``=(2x-1)(2x-1+3-x)``=(2x-1)(x+2)`
`a)`
Sửa lại đề bài : `x^2 + 2x`
` = x (x+2)`
Hoặc nếu có biến `y` thì có thể sửa đề thành :
`x^2 + 2xy + y^2 = (x+y)^2`
`b)`
`(3-2x)(5-x) - 2(x-5)^2`
` = (3-2x)(5-x) - 2(5-x)^2`
` = (5-x) [ (3-2x) - 2 (5-x)]`
` = (5-x) (3-2x - 10 + 2x)`
`= -7 (5-x)`
`c)`
`(2x-1)^2 - (3-x)(1-2x)`
`= (1-2x)^2 - (3-x)(1-2x)`
` = (1-2x) [ (1-2x) - (3-x)]`
` = (1-2x) (1 - 2x - 3 + x)`
` = (1-2x)(-2-x)`
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tìm x, biết (làm thế nào để làm bài này)
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