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(x-3)^3-(x+3)^3=x3-27
(1/2a+b)^3+(1/2a-b)^3=1/8a3-b3
mk chỉ làm đc 2 câu này thui
a: \(VT=x^2-25-x^2+4x-4-7x^2+x^3+1\)
\(=x^3-7x^2+4x-28\)
\(VP=x^3+9x^2+27x+27-x^3-9x^2=27x+27\)
=>\(x^3-7x^2-23x-55=0\)
=>\(x\in\left\{9.89\right\}\)
b: \(\Leftrightarrow4x^2+12x+9+x^2-1-5x^2-20x-20=-\left(x^2-4x-5\right)+x^2+8x+16\)
=>\(-8x-12=-x^2+4x+5+x^2+8x+16\)
=>-8x-12=12x+21
=>-20x=33
=>x=-33/20
a, \(\left(x+2\right)^2-\left(x+3\right)\left(x-3\right)+10=x^2+4x+4-x^2+9+10=4x+23\)
b, \(\left(5-x\right)^2+\left(x+5\right)^2-\left(2x+10\right)\left(x-5\right)=25-10x+x^2+x^2+10x+25-2x^2+50=100\)
a) ( x + 2 )2 - ( x + 3 )( x - 3 ) + 10
= x2 + 4x + 4 - ( x2 - 9 ) + 10
= x2 + 4x + 4 - x2 + 9 + 10
= 4x + 23
b) ( x + 1 )2 + ( x - 2 )( x + 3 ) - 4x
= x2 + 2x + 1 + x2 + x - 6 - 4x
= 2x2 - 2x - 5
c) ( x - 2 )( x + 2 ) - ( x - 3 )( x + 1 )
= x2 - 4 - ( x2 - 2x - 3 )
= x2 - 4 - x2 + 2x + 3
= 2x - 1
d) ( x + 4 )2 + ( x + 5 )( x - 5 ) - 2x( x + 1 )
= x2 + 8x + 16 + x2 - 25 - 2x2 - 2x
= 6x - 9
e) ( 5 - x )2 + ( x + 5 )2 - ( 2x + 10 )( x - 5 )
= 25 - 10x + x2 + x2 + 10x + 25 - ( 2x2 - 50 )
= 2x2 + 50 - 2x2 + 50
= 100
f) ( x - 2 )2 + ( x + 1 )2 + 2( x - 2 )( -1 - x )
= x2 - 4x + 4 + x2 + 2x + 1 + 2( -x2 + x + 2 )
= 2x2 - 2x + 5 - 2x2 + 2x + 4
= 9
g) ( 3x - 5 )2 - 2( 3x - 5 )( 3x + 5 ) + ( 3x + 5 )2
= [ ( 3x - 5 ) - ( 3x + 5 ) ]2
= ( 3x - 5 - 3x - 5 )2
= ( -10 )2 = 100
h) ( y - 3 )( y + 3 )( y2 + 9 ) - ( y2 + 2 )( y2 - 2 )
= ( y2 - 9 )( y2 + 9 ) - [ ( y2 )2 - 4 ]
= [ ( y2 )2 - 81 ] - y4 + 4
= y4 - 81 - y4 + 4
= -77
\(\left(x-2\right)^3:\left(2-x\right)-x^2-5\)
\(=-\left(x-2\right)^2-x^2-5\)
\(=-x^2+4x-4-x^2-5\)
\(=-2x^2+4x-9\)