Bạn nên viết đề bằng công thức toán (biểu tượng $\sum$ góc trái khung soạn thảo) để mọi người hiểu đề của bạn hơn nhé.

b: \(B=\dfrac{\left(x+y\right)^2-z^2}{x+y+z}\)

\(=\dfrac{\left(x+y-z\right)\left(x+y+z\right)}{x+y+z}\)

=x+y-z

c: 
ĐKXĐ: x<>1

\(C=\dfrac{x^2-6x+5}{x^2-2x+1}\)

\(=\dfrac{\left(x-1\right)\left(x-5\right)}{\left(x-1\right)^2}\)

\(=\dfrac{x-5}{x-1}\)

bn nào jup mk nhanh vs mk đag cần gấp

(x+y)^2-(x-y)^2-4(x-1)y

=(x+y-x+y)(x+y+x-y)-4xy+4y

=2x*2y-4xy+4y

4xy-4xy+4y

=4y

\(\frac{x^2+y^2-1+2xy}{x^2-y^2+1+2x}\)

\(=\frac{\left(x+y\right)^2-1}{\left(x-1\right)^2-y^2}\)

\(=\frac{\left(x+y-1\right)\left(x+y+1\right)}{\left(x-1-y\right)\left(x-1+y\right)}\)

\(=\frac{x+y+1}{x-y-1}\)

sai đề rồi nhé , đề phải là :

\(\frac{x^3-y^3+z^3+3xyz}{\left(x+y\right)^2+\left(y+z\right)^2+\left(z-x\right)^2}\)

\(=\frac{\left(x-y\right)^3+3xy.\left(x-y\right)+z^3+3xyz}{x^2+2xy+y^2+y^2+2yz+z^2+z^2-2xz+x^2}\)

\(=\frac{\left(x-y+z\right).\left[\left(x-y\right)^2-\left(x-y\right).z+z^2\right]+3xy.\left(x-y+z\right)}{2x^2+2y^2+2z^2+2xy+2yz-2xz}\)

\(=\frac{\left(x-y+z\right).\left(x^2-2xy+y^2-xz+yz+z^2+3xy\right)}{2.\left(x^2+y^2+z^2+xy+yz-xz\right)}\)

\(=\frac{\left(x-y+z\right).\left(x^2+y^2+z^2+xy+yz-xz\right)}{2.\left(x^2+y^2+z^2+xy+yz-xz\right)}\)

\(=\frac{x-y+z}{2}\)

\(a,\dfrac{21x^2y^3}{24x^3y^2}=\dfrac{7y}{8x}\)

\(b,\dfrac{15xy^3\left(x^2-y^2\right)}{20x^2y\left(x+y\right)^2}=\dfrac{15xy^3\left(x-y\right)\left(x+y\right)}{20x^2y\left(x+y\right)^2}=\dfrac{3y^2\left(x-y\right)}{4x\left(x+y\right)}=\dfrac{3xy^2-3y^3}{4x^2+4xy}\)

a) Ta có: \(\dfrac{21x^2y^3}{24x^3y^2}\)

\(=\dfrac{21x^2y^3:3x^2y^2}{24x^3y^2:3x^2y^2}\)

\(=\dfrac{7y}{8x}\)

1. = \(\dfrac{x+y}{x-y}\)
2. = \(\dfrac{x}{x+3}\)

\(\dfrac{5xy^3\left(x-y\right)}{10xy\left(x-y\right)^3}=\dfrac{y^2}{2\left(x-y\right)^2}\)

\(\dfrac{5xy^3\left(x-y\right)}{10xy\left(x-y\right)^3}=\dfrac{y^2}{2\left(x-y\right)^2}\)