a, 2x(2x-1)^2-3x(x+3)(x-3)-4x(x+1)^2 b, (a-b+c)^2-(b-c)^2+2ab-2ac c, (3x+1)^2-2(3x+1)(3x+5)+(3x+5)^2 d, (2x+y)^2-(y-2x)^2 e, (3x+2)^2+2(2+3x)(1-2y)+(2y-1)^2
2 câu trả lời
`a) ( a + b + c ) 2 + ( a + b - c ) 2 -2 xx ( a+b) 2`
`2a+2b+2x+2a+2b-2c-2.(2a+2b)`
`2a+2b+2c+2a+2b-2c-4a-4b`
`4a+4b-4a-4b=0`
`b) 2x.( 2x -1 ) 2 -3x.( x+3 )( x-3) - 4x.(x+1).2`
`2x.(4x-2)-3x2-9x-3x2+9x-4x(2x+2)`
`8x2-4x-3x2-9x-3x2+9x-8x2-8x`
`-12x-3x2`
`c) ( a-b+c).2 -(b-c).2 + 2ab - 2ac`
`2a-2b+2c-2b+2c+2ab-2ac`
`2a-4b+4c+2ab-2ac`
`d) (3x+1).2 - 2(3x+1)( 3x+5 )+(3x+5).2`
`6x+2-6x-2-6x-10+6x+10=0`
Đáp án: a) ( a + b + c ) 2 + ( a + b - c ) 2 -2 x ( a+b) 2
2a+2b+2x+2a+2b-2c-2.(2a+2b)
2a+2b+2c+2a+2b-2c-4a-4b
4a+4b-4a-4b=0
b) 2x.( 2x -1 ) 2 -3x.( x+3 )( x-3) - 4x.(x+1).2
2x.(4x-2)-3x2-9x-3x2+9x-4x(2x+2)
8x2-4x-3x2-9x-3x2+9x-8x2-8x
-12x-3x2
c) ( a-b+c).2 -(b-c).2 + 2ab - 2ac
2a-2b+2c-2b+2c+2ab-2ac
2a-4b+4c+2ab-2ac
d) (3x+1).2 - 2(3x+1)( 3x+5 )+(3x+5).2
6x+2-6x-2-6x-10+6x+10=0
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