Công thức tính diện tích hình chữ nhật là :

S = ( a + b ) x 2 

=> (Chiều dài + chiều rộng ) x 2 

a)\(\frac{3y}{4x}+\frac{5y}{4x}=\frac{3y+5y}{4x}=\frac{8y}{4x}=\frac{2y}{x}\)

b)\(\frac{x^2+1}{2x-4}-\frac{7x}{2-x}=\frac{x^2+1}{2\left(x-2\right)}-\frac{-7x}{x-2}\)

\(=\frac{x^2+1}{2\left(x-2\right)}-\frac{-7x\times2}{\left(x-2\right)\times2}=\frac{x^2+1+14x}{2\left(x-2\right)}\)

\(a,\frac{8x^2y^5}{10x^3y^4}=\frac{4y}{5x}\)

\(b,\frac{x^2-xy}{4xy-4y^2}=\frac{x\left(x-y\right)}{4y\left(x-y\right)}=\frac{x}{4y}\)

\(A=\frac{x^2-2x+1}{x-1}+\frac{x^2+2x+1}{x+1}-1\)

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

\(A=\left(x-1\right)+\left(x+1\right)-1\)

thay x = 1 vào A

\(\Rightarrow A=\left(1-1\right)+\left(1+1\right)-1\)

\(A=1\)

ĐKXĐ: \(x\ne0;x\ne\frac{1}{2}\)

\(\frac{2x^2+1}{4x^2-2x}+\frac{3}{2x}-\frac{3-3x}{2x-1}\)

\(=\frac{2x^2+1}{4x^2-2x}+\frac{3}{2x}-\frac{6x-6x^2}{4x^2-2x}\)

\(=\frac{8x^2-6x+1}{4x^2-2x}+\frac{3}{2x}=\frac{8\left(x-\frac{1}{2}\right)\left(x-\frac{1}{4}\right)}{4x\left(x-\frac{1}{2}\right)}+\frac{3}{2x}\)

\(=\frac{8x-2}{4x}+\frac{3}{2x}=\frac{8x-2}{4x}+\frac{6}{4x}=\frac{8x-2+6}{4x}\)

\(=\frac{8x+4}{4x}=1+\frac{4x+4}{4x}=2+\frac{4}{4x}=2+\frac{1}{x}\)

Ơ bài t có gì sai????lại là bọn dis dạo nữa cơ à? Ok,ok cho chúng m dis,t cx méo quan tâm.Và t biết bài t đúng!

\(\frac{x^2+4y^2-4xy-4}{2x^2-4xy+4x}=\frac{\left(x^2-4xy+4y^2\right)-4}{2x.\left(x-2y+2\right)}.\)

\(=\frac{\left(x-2y\right)^2-4}{2x.\left(x-2y+2\right)}=\frac{\left(x-2y+2\right).\left(x-2y-2\right)}{2x.\left(x-2y+2\right)}\)

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

chúc bn học tốt!