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Có x = 13 : 10 x 100 = 130
y = 13 : 20 x 100 = 65
=> 5x + 10y = (5 x 130) + (10 x 65) = 650 + 650 = 1300
x = 13 : 10% = 130
y = 13 : 20% = 65
Rùi mk thay x, y vào biểu thức đx cho và tình thui
Bài này trở thành đơn giản, nhỉ ?
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\frac{3x}{5x+5y}-\frac{x}{10x-10y}\)
\(=\frac{3x}{5.\left(x+y\right)}-\frac{x}{10\left(x-y\right)}\)
\(=\frac{2.3x\left(x-y\right)}{2.5.\left(x+y\right)\left(x-y\right)}-\frac{\left(x+y\right).x}{10.\left(x+y\right)\left(x-y\right)}\)
\(=\frac{6x^2-6xy-x^2-xy}{10\left(x+y\right)\left(x-y\right)}\)
\(=\frac{5x^2-7xy}{10\left(x+y\right)\left(x-y\right)}\)
Tham khảo nhé~
![](https://rs.olm.vn/images/avt/0.png?1311)
\(5x^2-5y^2-10x+10y\)
\(=5\left(x^2-y^2\right)-10\left(x+y\right)\)
\(=5\left(x+y\right)\left(x-y\right)+10\left(x+y\right)\)
\(=\left(x+y\right)\left(5\left(x-y\right)+10\right)\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\frac{3x}{5x+5y}-\frac{x}{10x-10y}\)
= \(\frac{3x\left(x-y\right)}{5.2.\left(x+y\right)\left(x-y\right)}-\frac{x\left(x+y\right)}{10\left(x^2-y^2\right)}\)
= \(\frac{3x^2-3xy-x^2-xy}{10\left(x^2-y^2\right)}\)
= \(\frac{3x\left(x-y\right)}{10\left(x^2-y^2\right)}\)
= \(\frac{3x}{10\left(x+y\right)}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
3(x2-2xy+y2):10(x-y)
3(x-y)2:10(x-y)
3(x-y):10
5(x2-xy+y2):(x+y)(x2-xy+y2)
5:x+y
ở nơi 5y thiếu ^2 nhé
![](https://rs.olm.vn/images/avt/0.png?1311)
\(1)4x^2-25+\left(2x+7\right).\left(5.2x\right)\)
\(=\left(2x\right)^2-5^2-\left(2x+7\right).\left(2x-5\right)\)
\(=\left(2x.5\right)\left(2x+5\right).\left(2x+7\right)\left(2x-5\right)\)
\(=\left(2x-5\right)\left(2x+5-2x+7\right)\)
\(=\left(2x-5\right).12\)
\(2)3x+4-x^2-4x\)
\(=3(x+4)-\left(x+4\right)\)
\(=\left(3-x\right)\left(x+4\right)\)
\(3)5x^2-2y^2-10x+10y\)
\(=5\left(x^2-y^2\right)-10\left(x-4\right)\)
\(=5\left(x-y\right)\left(x+y\right)-10\left(x-y\right)\)
\(=\left(x-y\right)[5(x+y)-10]\)
Còn lại bn lm nốt nha!
![](https://rs.olm.vn/images/avt/0.png?1311)
b, 3x^2+5y-3xy-5x
=(3x^2-3xy)+(5y-5x)
=3x(x-y)+5(y-x)
=3x(x-y)-5(x-y)
=(x-y)(3x-5)
a: =5(x+y-2x^2-2y^2)
b: =3x(x-y)-5(x-y)
=(x-y)(3x-5)
Đề sai bạn ơi
tinh 3/5x+5y-x/10x-10y