Bài 1: Thu gọn biểu thức
a) 6( 2x – 1 ) ² + 5( x – 2 )( x + 3 ) – 2( 5 – 2x ) ²
b) ( 9x – 1 ) ² + ( 1 – 5x ) ² + 2( 9x – 1 )( 1 – 5x )
c) ( x ² – 5x + 1 ) ² + 2( 5x – 1 )(x ² – 5x + 1 ) + ( 5x -1 ) ²
Làm nhanh hộ mình với ạ, ai làm đầy đủ, giải nhanh mình sẽ vote câu trả lời hay nhất cho
`a) 6(2x-1)^2 + 5(x-2)(x+3) – 2(5-2x)^2`
`= 6(4x^2 – 4x + 1) + 5(x-2)(x+3) – 2(5-2x)^2`
`= 6(4x^2-4x+1) + 5(x-2)(x+3) – 2(25-20x+4x^2)`
`= 24x^2 – 24x + 6 + 5x^2 + 5x – 30 – 2(25-20x+4x^2)`
`= 24x^2 – 24x + 6 + 5x^2 – 30 – 50 + 40x – 8x^2`
`= 21x^2 + 21x – 74`
`b) (9x-1)^2 + (1-5x)^2 + 2(9x-1)(1-5x)`
`= 81x^2 – 18x + 1 + (1-5x)^2 + 2(9x-1)(1-5x)`
`= 81x^2 – 18x + 1 + 1 – 10x + 25x^2 +2(9x-1)(1-5x)`
`= 81x^2 – 18x + 1 + 1 – 10x + 25x^2 – 90x^2 + 28x – 2`
`= 16x^2`
`c) (x^2-5x+1)^2 + 2(5x-1)(x^2-5x+1)+(5x-1)^2`
`= (x^2-5x+1)(x^2-5x+1) + 2(5x-1)(x^2-5x+1) + 25x^2 – 10x + 1`
`= x^4 – 10x^3 + 27x^2 – 10x + 1 + 2(5x-1)(x^2-5x+1)+25x^2 – 10x + 1`
`= x^4 – 10x^3 + 27x^2 – 10x + 1 + 10x^3 – 52x^2 + 20x – 2 + 25x^2 – 10x + 1`
`= x^4`
`a)6(2x-1)²+5(x-2)(x+3)-2(5-2x)²`
`=6(4x²-4x+1)+(5x-10)(x+3)-2(25-20x+4x²)`
`=24x²-24x+6+5x²+15x-10x-30-50+40x-8x²`
`=(24x²+5x²-8x²)+(-24x+15x-10x+40x)+(6-30-50)`
`=21x²+21x-74`
`b)(9x-1)²+(1-5x)²+2(9x-1)(1-5x)`
`=81x²-18x+1+1-10x+25x²+(18x-2)(1-5x)`
`=81x²-18x+1+1-10x+25x²+18x-90x²-2+10x`
`=(81x²+25x²-90x²)+(-18x-10x+18x+10x)+(1+1-2)`
`=16x²`
`c)(x²-5x+1)²+2(5x-1)(x²-5x+1)+(5x-1)²`
`=(x²-5x+1+5x-1)²`
`=(x²)²`
`=x^4`