Đáp án:
`6 , -(x - 3)^2`
`7, (x + 2y)^2`
`8, 4xy`
`9, 4x(2x + 1)`
`10 , (5x - 4)(8 - x)`
Giải thích các bước giải:
`6 , 6x - 9 - x^2`
` = -(x^2 - 6x + 9)`
` = -(x - 3)^2`
`7 , x^2 + 4y^2 + 4xy`
` = (x + 2y)^2`
`8, (x + y)^2 - (x - y)^2`
` = (x + y - x + y)(x + y + x - y)`
` = 4xy`
`9, (3x + 1)^2 - (x + 1)^2`
` = (3x + 1 - x - 1)(3x + 1 + x + 1)`
` = 2x(4x + 2)`
` = 4x(2x + 1)`
`10 , 4(x + 1)^2 - 9(2 - x)^2`
` = ( 2(x + 1) ) ^2 - ( 3(2 - x) )^2`
` = (2x + 2)^2 - (6 - 3x)^2`
` = (2x + 2 - 6 + 3x)(2x + 2 + 6 - 3x)`
` = (5x - 4)(8 - x)`
