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a. gọi phần đầu đấy là A nhá, để đỡ cần viết lại
A=...............
= (3x+5)2 + ( 3x-5)2 - 9x2 -4
= (9x2 +30x + 25 ) + ( 9x2 -30x+ 25 ) - 9x2 -4
= 9x2 +30x + 25 + 9x2 -30x+25-9x2 -4
= 9x2 + 46
sai thì thôi nhé. bạn nên kiểm tra lại
d. (2x-1)*(4x2 + 2x +1 ) - 8x*( x2 +1) - 5
= 8x3 -1 - 8x3 -8x-5
= -8x-6
= -2(4x+3)
sai nhé. bạn nên kiểm tra lại
a: \(=4x^2+20x+25+4x^2-20x+25-\left(4x^2-1\right)\)
\(=8x^2+50-4x^2+1=4x^2+51\)
b: \(=8a^3+12a^2b+6ab^2+b^3+8a^3-12a^2b+6ab^2-b^3-16a^3\)
\(=12ab^2\)
c: \(\left(2x-1\right)^3-\left(x-2\right)\left(x^2+2x+4\right)-7x^3-2x\)
\(=\left(2x-1\right)^3-x^3+8-7x^3-2x\)
\(=8x^3-12x^2+6x-1-8x^3-2x+8\)
\(=-12x^2+4x+7\)
d: \(\left(x+1\right)^2-\left(x-1\right)^2-3\left(x+1\right)\left(x-1\right)\)
\(=x^2+2x+1-\left(x^2-2x+1\right)-3\left(x^2-1\right)\)
\(=x^2+2x+1-x^2+2x-1-3x^2+3\)
\(=-3x^2+4x+3\)
\(A=2x^3+3\left(x-1\right)\left(x+1\right)-5x\left(x+1\right)\)
\(=2x^3+3\left(x^2-1\right)-5x^2-5x\)
\(=2x^3+3x^2-3-5x^2-5x\)
\(=2x^3-2x^2-5x-3\)
\(B=\left(5-2x\right)^3-\left(3x+5\right)\left(5-3x\right)\)
\(=125-150x+60x^2-8x^3-\left(25-9x^2\right)\)
\(=125-150x+60x^2-8x^3-25+9x^2\)
\(=100-15x+69x^2-8x^3\)
\(C=\left(3x+1\right)^2-\left(2x-1\right)^2\)
\(=\left(3x+1-2x+1\right)\left(3x+1+2x-1\right)\)
\(=\left(x+2\right).5x\)
\(D=\left(2x+1\right)^2+\left(3-x\right)^2-2\left(2x+1\right)\left(3-x\right)\)
\(=\left(2x+1-3+x\right)^2\)
\(=\left(3x-2\right)^2\)
\(E=\left(x-2\right)^3-x\left(x+1\right)\left(x-1\right)+6x\left(x-3\right)\)
\(=x^3-6x^2+12x-8+x\left(x^2-1\right)+6x^2-18x\)
\(=x^3-6x^2+12x-8+x^3-x+6x^2-18x\)
\(=-7x-8\)
\(F=\left(x-1\right)^3-3\left(1-x\right)\left(x+1\right)-\left(x^2+x+1\right)\left(x-1\right)-3x\)
\(=x^3-3x^2+3x-1-3\left(1-x^2\right)-\left(x^3-1\right)-3x\)
\(=x^3-3x^2+3x-1-3+3x^2-x^3+1-3x\)
\(=-3\)
Trả lời:
a, ( x + y )2 + ( x - y )2 - 2x2 = x2 + 2xy + y2 + x2 - 2xy + y2 - 2x2 = 2y2
b, 2( x - y )( x + y ) + ( x + y )2 + ( x - y )2
= 2( x2 - y2 ) + x2 + 2xy + y2 + x2 - 2xy + y2
= 2x2 - 2y2 + x2 + 2xy + y2 + x2 - 2xy + y2
= 4x2
c, ( x - 3 )( x + 3 ) - ( x - 5 )
= x2 - 9 - x + 5
= x2 - x - 4
d, ( 2x + 1 )2 + 2( 2x + 1 )( 3x - 1 ) + ( 3x - 1 )2
= 4x2 + 4x + 1 + ( 4x + 2 )( 3x - 1 ) + 9x2 - 6x + 1
= 4x2 + 4x + 1 + 12x2 - 4x + 6x - 2 + 9x2 - 6x + 1
= 25x2
e, ( 3x + 5 )2 - 2( 3x + 5 )( 2x + 5 ) + ( 2x + 5 )2
= 9x2 + 30x + 25 + ( - 6x - 10 )( 2x + 5 ) + 4x2 + 20x + 25
= 9x2 + 30x + 25 - 12x2 - 30x - 20x - 50 + 4x2 + 20x + 25
= x2
\(a,\left(6x+1\right)\left(x+2\right)-2x\left(3x-5\right)\)
\(=6x^2+12x+x+2-6x^2+10x\)
\(=23x+2\)
a) (6x + 1)(x + 2) - 2x(3x - 5)
= 6x2 + 12x + x + 2 - 6x2 + 10x
= (6x2 - 6x2) + (12x + x + 10x) + 2
= 23x + 2
b) (2x - 1)2 - (2x - 3)(2x + 3)
= 4x2 - 4x + 1 - 4x2 + 9
= (4x2 - 4x2) - 4x + (1 + 9)
= -4x + 10
c) (2x - 3)3 - (3x + 1)(5 - 4x) - 16x2
= 8x3 - 36x2 + 54x - 15x + 12x2 - 5 + 4x - 16x2
= 8x3 - (36x2 - 12x2 + 16x2) + (54x - 15x + 4x) - 5
= 8x3 - 40x2 + 43x - 5
d) (3x + 2) - (x - 5) - x(3x - 13)
= 3x + 2 - x + 5 - 3x2 + 13x
= (3x - x + 13x) + (2 + 5) - 3x2
= 15x + 7 - 3x2
a) \(A=\left(5-x\right)\left(x+5\right)-2\left(x-1\right)\left(x-3\right)-3\left(x-2\right)^2\)
\(=\left(5-x\right)\left(5+x\right)-\left(2x-2\right)\left(x-3\right)-3\left(x^2-2.2x+2^2\right)\)
\(=\left(5^2-x^2\right)-\left[2x\left(x-3\right)-2\left(x-3\right)\right]-3\left(x^2-4x+4\right)\)
\(=25-x^2-\left[\left(2x^2-6x\right)-\left(2x-6\right)\right]-3x^2+12x-12\)
\(=25-x^2-\left(2x^2-6x-2x+6\right)-3x^2+12x-12\)
\(=25-x^2-2x^2+6x+2x-6-3x^2+12x-12\)
\(=7+20x-6x^2\)
b/ \(B=\left(3-2x\right)\left(x-2\right)+\left(2x-5\right)^2-\left(x-4\right)\)
\(=3\left(x-2\right)-2x\left(x-2\right)+\left[\left(2x\right)^2-2.2x.5+5^2\right]-x+4\)
\(=3x-6-2x^2+4x+4x^2-20x+25-x+4\)
\(=23-14x+2x^2\)
c/ \(C=\left(x-4\right)\left(x-2\right)-3\left(x-2\right)\left(3-2x\right)-\left(2x+1\right)^2\)
\(=x\left(x-2\right)-4\left(x-2\right)-\left(3x-6\right)\left(3-2x\right)-\left[\left(2x\right)^2+2.2x.1+1^2\right]\)
\(=x^2-2x-4x+8-\left[3x\left(3-2x\right)-6\left(3-2x\right)\right]-4x^2-4x-1\)
\(=x^2-2x-4x+8-\left(9x-6x^2-18+12x\right)-4x^2-4x-1\)
\(=x^2-2x-4x+8-9x+6x^2+18-12x-4x^2-4x-1\)
\(=25-31x+3x^2\)
d/ \(D=2\left(x-1\right)^2-3\left(x-1\right)\left(x+2\right)-\left(2x+1\right)^2\)
\(=2.\left(x^2-2x+1\right)-\left(3x-3\right)\left(x+2\right)-\left[\left(2x\right)^2+2.2x+1\right]\)
\(=2x^2-4x+2-\left[3x\left(x+2\right)-3\left(x+2\right)\right]-\left(4x^2+4x+1\right)\)
\(=2x^2-4x+2-\left(3x^2+6x-3x-6\right)-\left(4x^2+4x+1\right)\)
\(=2x^2-4x+2-3x^2-6x+3x+6-4x^2-4x-1\)
\(=7-11x-5x^2\)
P/s: Ko chắc ạ!
a: =x^2+2x-15-x^2+4
=2x-11
b: =x^2-4x+4+x^2+6x+9-2(x^2-1)
=2x^2+2x+13-2x^2+2
=2x+15
c: \(=x^2-4x+4+x^3-1-x^3+4x\)
=x^2+3
d: \(=\left(2x+5-2x+1\right)^2=6^2=36\)
e: \(=x^3+1-x^3+1-x^2=2-x^2\)