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\(A=\left(3x-2\right)^2-\left(x+3\right)^2\)
\(=\left(3x-2+x+3\right)\left(3x-2-x-3\right)\)
\(=\left(4x+1\right)\left(2x-5\right)\)
\(B=\left(x+2y+3z\right)^2-\left(x-2y-3z\right)^2\)
\(=\left(x+2y+3z-x+2y+3z\right)\left(x+2y+3z+x-2y-3z\right)\)
\(=2x\left(4y+6z\right)\)
\(=4x\left(2y+3z\right)\)
a. ta có :
\(\left(x+y\right)^2+\left(x-y\right)^2=4^2+\left(-5\right)^2\) hay \(2\left(x^2+y^2\right)=16+25\Leftrightarrow x^2+y^2=\frac{41}{2}\)
v. ta có : \(\left(x+y\right)^2-\left(x-y\right)^2=4^2-5^2\) hay \(4xy=-9\Leftrightarrow xy=-\frac{9}{4}\)
mà \(x^3+y^3=\left(x+y\right)^3-3xy\left(x+y\right)=4^3-3.\left(-\frac{9}{4}\right).4=64+27=91\)
c.\(x^4+y^4=\left(x^2+y^2\right)^2-2x^2y^2=\left(\frac{41}{2}\right)^2-2\left(-\frac{9}{4}\right)^2=\frac{3281}{8}\)
x+y+x-y=4-5=-1
2x=-1
x=-1/2
y=4+1/2=9/2
a)x2+y2=(-1/2)2+(9/2)2
=1/4+81/4
=21,25
b)x3+y3=(-1/2)3+(9/2)3
= -1/8 + 729/8
=91
c)x4+y4=-(1/2)4+(9/2)4
=1/16+6561/16
=6562/16
=410,125
a)
(x3 – 3x2+3x-1) – (x3+9) +(3x2-12) = 2
3x-22 = 2
3x =24
=> x= 8
b)
x3+6x2+12x+8-6x2-x3-x2+x2 = 5
12x+8 = 5
12x = -3
=>x = -1/4
a) ( x - 1 )3 - ( x + 3 )(x2 - 3x + 9 ) + 3( x2 - 4 ) = 2
(x3-3x2\(\times\)1+3x\(\times\)12-13)-(x3+33)+(3x2-3\(\times\)4)=2
x3-3x2+3x-1-x3-9+3x2-12=2
3x-40=2
3x=42
x=14
b ) ( x + 2 )3 - 6x2 - x2 ( x + 1 ) + x2 = 5
(x3+3\(\times\)2x2+3x\(\times\)22+23)-6x2-(x3+x2)+x2=5
x3+6x2+12x+8-6x2-x3-x2+x2=5
12x+8=5
12x=\(-\)3
x=\(-\frac{1}{4}\)
bài dễ mà 
\(\Leftrightarrow x^2-10+25-x^2+12x+36+10=0\)
\(\Leftrightarrow2x+71=0\)
\(\Leftrightarrow2x=-71\)
\(\Leftrightarrow x=\frac{-71}{2}\)
[ (x - 5)2 - (x - 6)2 ] + 10 =0
[(x-5)+(x-6)].[(x-5)-(x-6)] = -10
(2x-11).1 = -10
2x =1
x = 0,5
cách làm là như thế còn ko biết mk có tính sai ko!!!!