25-x^2+6xy-9y^2
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\(=\left(x-3y\right)^2-25=\left(x-3y-5\right)\left(x-3y+5\right)\)
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\(a^2-b^2-5a+5b=\left(a+b\right)\left(a-b\right)-5\left(a-b\right)=\left(a+b-5\right)\left(a-b\right)\)
\(x^2-6xy+9y^2-25=\left(x-3y\right)^2-5^2=\left(x-3y+5\right)\left(x-3y-5\right)\)
\(49-x^2-y^2+2xy=7^2-\left(x-y\right)^2=\left(7-x+y\right)\left(7+x-y\right)\)
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\(=\dfrac{4}{\left(x-3y\right)\left(x+3y\right)}\cdot\pm\left(2\sqrt{2}\right)\cdot y\cdot\left(x-3y\right)\)
\(=\dfrac{\pm8\sqrt{2}\cdot y}{x+3y}\)
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a) ( x-3y ) ( x + 1 )
b) ( x+y+5 ) ( x+y-5 )
c) ( x-5 ) ( x+2 )
Hk tốt
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\(\dfrac{x^2-9y^2}{x^2-6xy+9y^2}\) tại x = 1 , y = -\(\dfrac{2}{3}\)
= \(\dfrac{x^2-\left(3y\right)^2}{\left(x-3y\right)^2}\)
= \(\dfrac{\left(x-3y\right)\left(x+3y\right)}{\left(x-3y\right)}\)
= (x + 3y)
Thay x = 1 , y = -\(\dfrac{2}{3}\) vào
x + 3y
= 1 +3 . -\(\dfrac{2}{3}\)
= -1
Chúc bạn học tốt
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a) \(x^3+8y^3+4x+8y\)
\(=x^3-2x^2y+4xy^2+4x+2x^2y-4xy^2+8y^3+8y\)
\(=\left(x^3-2x^2y+4xy^2+4x\right)+\left(2x^2y-4x^2y+8y^3+8y\right)\)
\(=x\left(x^2-2xy+4y^2+4\right)+2y\left(x^2-2xy+4y^2+4\right)\)
\(=\left(x^2-2xy+4y^2+4\right)\left(x+2y\right)\)
b) \(x^2+6xy+9y^2+5x+15y\)
\(=\left(x^2+6xy+9y^2\right)+\left(5x+15y\right)\)
\(=\left(x+3y\right)^2+5\left(x+3y\right)\)
\(=\left(x+3y\right)\left(x+3y+5\right)\)
c) \(25-x^2+2xy-y^2\)
\(=25-\left(x^2-2xy+y^2\right)\)
\(=25-\left(x-y\right)^2\)
\(=5^2-\left(x-y\right)^2\)
\(=\left(5+x-y\right)\left(5-x+y\right)\)
25 - x2 + 6xy - 9y2
= 25 - (x2 - 6xy + 9y2)
= 25 - (x2 - 6xy + 3y2)
= 52 - (x - 3)2
= [5 + (x - 3)] [5 - (x - 3)]
= (5 + x - 3) (5 - x + 3)
#Học tốt!!!
~NTTH~
25 - x2 + 6xy - 9y2
= 25 - (x2 - 6xy + 9y2)
= 25 - (x2 - 6xy + 3y2)
= 52 - (x - 3)2
= [5 + (x - 3)] [5 - (x - 3)]
= (5 + x - 3) (5 - x + 3)
#Học tốt!!!
~NTTH~