\(\frac{x^2+25y^2}{x^2-25y^2}-\frac{10xy}{x^2-25y^2}\)
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c: \(=\dfrac{\left(x+2\right)^2}{\left(x-5y\right)^2}\cdot\dfrac{\left(x-5y\right)\left(x+5y\right)}{\left(x-2\right)\left(x+2\right)}\)
\(=\dfrac{\left(x+2\right)\left(x+5y\right)}{\left(x-5y\right)\left(x-2\right)}\)
\(25-x^2-10xy-25y^2\)
\(=25-x^2-10xy-25y^2\)
\(=25-\left(x^2+10xy+25y^2\right)\)
\(=25-\left(x+5y\right)^2\)
\(=5^2-\left(x+5y\right)^2\)
\(=\left(5-x-5y\right)\left(5+x+5y\right)\)
Sửa đề: 25-x^2-10xy-25y^2
=25-(x^2+10xy+25y^2)
=25-(x+5y)^2
=(5-x-5y)(5-x+5y)
\(x^2-10xy+25y^4\\ =x^2-2.5.x.y+\left(5y^2\right)^2\\ =\left(x-5y^2\right)^2\)
Thay \(x=105,y=5\) vào biểu thức ta được:
\(\left(105-5.5^2\right)^2\\ =\left(105-5.25\right)^2\\ =\left(-23\right)^2\\ =529\)
\(\left(\frac{5x+y}{x^2-5xy}+\frac{5x-y}{x^2+5xy}\right).\frac{x^2-25y^2}{x^2+y^2}\)
\(=\left(\frac{5x+y}{x\left(x-5y\right)}+\frac{5x-y}{x\left(x+5y\right)}\right).\frac{\left(x-5y\right)\left(x+5y\right)}{x^2+y^2}\)
\(=\frac{\left(5x+y\right)\left(x+5y\right)+\left(5x-y\right)\left(x-5y\right)}{x\left(x-5y\right)\left(x+5y\right)}.\frac{\left(x-5y\right)\left(x+5y\right)}{x^2+y^2}\)
\(=\frac{10\left(x^2+y^2\right)}{x\left(x^2+y^2\right)}=\frac{10}{x}\)
\(\left(\frac{5x+y}{x^2-5xy}+\frac{5x-y}{x^2+5xy}\right).\frac{x^2-25y^2}{x^2+y^2}\)
\(=\left(\frac{5x+y}{x\left(x-5y\right)}+\frac{5x-y}{x\left(x+5y\right)}\right)\frac{\left(x-5y\right)\left(x+5y\right)}{x^2+y^2}\)
\(=\frac{\left(5x+y\right)\left(x+5y\right)+\left(5x-y\right)\left(x-5y\right)}{x\left(x-5y\left(x+4y\right)\right)}.\frac{\left(x-5y\right)\left(x+5y\right)}{x^2+y^2}\)
\(=\frac{10\left(x^2+y^2\right)}{x\left(x^2+y^2\right)}=\frac{10}{x}\)
\(\frac{x^2+25y^2-10xy}{x^2-25y^2}\)
\(\frac{\left(x-5y\right)^2}{\left(x-5y\right)\cdot\left(x+5y\right)}\)
\(\frac{x-5y}{x+5y}\)
đk: \(x\ne\pm5y\)
\(\frac{x^2+25y^2}{x^2-25y^2}-\frac{10xy}{x^2-25y^2}\)
\(=\frac{x^2+25y^2-10xy}{\left(x-5y\right)\left(x+5y\right)}\)
\(=\frac{\left(x-5y\right)^2}{\left(x-5y\right)\left(x+5y\right)}\)
\(=\frac{x-5y}{x+5y}\)