Tính \(y=\frac{1}{x^2-3x+2}+\frac{1}{x^2-5x+6}+...+\frac{1}{x^2-4015x+4030056}\)
Tính giá trị của biểu thức :
Q = \(\dfrac{1}{X^2+X}\) + \(\dfrac{1}{X^2+3X+2}\) +\(\dfrac{1}{X^2+5X+6}\) + ..................+\(\dfrac{1}{X^2+4015X+4030056}\)
Với x = \(\dfrac{2}{\sqrt{4-3\sqrt[4]{5}+2\sqrt{5}-\sqrt[4]{125}}}\)
Ta chứng minh: \(\sqrt[4]{5}\) là 1 nghiệm của phương trình
\(\dfrac{2}{\sqrt{4-3a+2a^2-a^3}}=a+1\)
\(\Leftrightarrow\dfrac{2}{4-3a+2a^2-a^3}=a^2+2a+1\)
\(\Leftrightarrow a\left(a^4-5\right)=0\)
\(\Rightarrow a=\sqrt[4]{5}\)
Từ đây ta suy ra được
\(x=\dfrac{2}{\sqrt{4-3\sqrt[4]{5}+2\sqrt{5}-\sqrt[4]{125}}}=1+\sqrt[4]{5}\)
Ta lại có:
\(Q=\dfrac{1}{x^2+x}+\dfrac{1}{x^2+3x+2}+\dfrac{1}{x^2+5x+6}+...+\dfrac{1}{x^2+4015x+4030056}\)
\(=\dfrac{1}{x\left(x+1\right)}+\dfrac{1}{\left(x+1\right)\left(x+2\right)}+\dfrac{1}{\left(x+2\right)\left(c+3\right)}+...+\dfrac{1}{\left(x+2007\right)\left(x+2008\right)}\)
\(=\dfrac{1}{x}-\dfrac{1}{x+1}+\dfrac{1}{x+1}-\dfrac{1}{x+2}+\dfrac{1}{x+2}-\dfrac{1}{x+3}+...+\dfrac{1}{x+2007}+\dfrac{1}{x+2008}\)
\(=\dfrac{1}{x}-\dfrac{1}{x+2008}=\dfrac{2008}{x^2+2008x}\)
Thế x vô nữa là xong
1,Thực hiện phép tính
a,\(\frac{3}{2x^2+2x}+\frac{2x-1}{x^2-1}-\frac{2}{x}\)
b,\(\frac{3x}{5x+5y}-\frac{x}{10x-10y}\)
c,\(\frac{5x^2-y^2}{xy}-\frac{3x-2y}{y}\)
d,\(\frac{3}{2x+6}-\frac{x-6}{2x^2+6x}\)
\(\frac{3x}{5x+5y}-\frac{x}{10x-10y}\)
\(=\frac{3x}{5\left(x+y\right)}-\frac{x}{10\left(x+y\right)}\)
\(=\frac{30x\left(x-y\right)-5x\left(x+y\right)}{5\left(x+y\right).10\left(x+y\right)}\)
\(=\frac{5x\left(5x-7y\right)}{50\left(x+y\right)\left(x-y\right)}\)
\(=\frac{x\left(5x-7y\right)}{\left(x+y\right)\left(x-y\right)}\)
chỗ cuối tớ sai
\(=\frac{x\left(5x-7y\right)}{10\left(x+y\right)\left(x-y\right)}\)
đây nha , e xin lỗi
a) \(\frac{3}{2x^2+2x}+\frac{2x-1}{x^2-1}-\frac{2}{x}=\frac{3}{2x\left(x+1\right)}+\frac{2x-1}{\left(x-1\right)\left(x+1\right)}-\frac{2}{x}\)
\(=\frac{3\left(x-1\right)+\left(2x-1\right)-2.2\left(x-1\right)\left(x+1\right)}{2x\left(x-1\right)\left(x+1\right)}\)
\(=\frac{3x-2x+4x^2-2x-4x^2+4x-4x+4}{2x\left(x-1\right)\left(x+1\right)}\)
\(=\frac{x+1}{2x\left(x-1\right)\left(x+1\right)}\)
\(=\frac{1}{2x\left(x-1\right)}\)
b) \(\frac{3x}{5x+5y}-\frac{x}{10x-10y}=\frac{3x}{5\left(x+y\right)}-\frac{x}{10\left(x-y\right)}\)
\(=\frac{3x.10\left(x-y\right)-x.5\left(x+y\right)}{50\left(x-y\right)\left(x+y\right)}\)
\(=\frac{30x\left(x-y\right)+5x\left(x+y\right)}{50\left(x-y\right)\left(x+y\right)}\)
\(=\frac{5x\left[6\left(x-y\right)-\left(x+y\right)\right]}{50\left(x-y\right)\left(x+y\right)}\)
\(=\frac{5x\left(5x-7y\right)}{50\left(x-y\right)\left(x+y\right)}\)
\(=\frac{x\left(5x-7y\right)}{10\left(x-y\right)\left(x+y\right)}\)
c) \(\frac{5x^2-y^2}{xy}-\frac{3x-2y}{y}=\frac{5x^2-y-x\left(3x-2y\right)}{xy}\)
\(=\frac{5x^2-y-3x^2+2xy}{xy}\)
\(=\frac{2x^2-y+2xy}{xy}\)
d) \(\frac{3}{2x+6}-\frac{x-6}{2x^2+6x}=\frac{3}{2\left(x+3\right)}-\frac{x-6}{2x\left(x+3\right)}\)
\(=\frac{3x-x+6}{2x\left(x+3\right)}\)
\(=\frac{2x+6}{2x\left(x+3\right)}\)
\(=\frac{2\left(x+3\right)}{2x\left(x+3\right)}\)
\(=\frac{2}{2x}=\frac{1}{x}\)
7,Thực hiện phép tính
a,\(\frac{4x+1}{2}-\frac{3x+2}{3}\)
b,\(\frac{x+3}{x^2-1}-\frac{1}{x^2+x}\)
c,\(\frac{3}{2x^2+2x}+\frac{2x-1}{x^2-1}-\frac{1}{2}\)
d,\(\frac{3x}{5x+5y}-\frac{x}{10x-10y}\)
e,\(\frac{5x^2-y^2}{xy}-\frac{3x-2y}{y}\)
f,\(\frac{3}{2x+6}-\frac{x-6}{2x^2+6x}\)
a, \(\frac{4x+1}{2}-\frac{3x+2}{3}=\frac{12x+3}{6}-\frac{6x+4}{6}=\frac{12x+3-6x-4}{6}=\frac{6x-1}{6}\)
b, \(\frac{x+3}{x^2-1}-\frac{1}{x^2+x}=\frac{x+3}{\left(x-1\right)\left(x+2\right)}-\frac{1}{x\left(x+1\right)}\)
\(=\frac{x\left(x+3\right)}{x\left(x-1\right)\left(x+1\right)}-\frac{x-1}{x\left(x-1\right)\left(x+1\right)}\)
\(=\frac{x^2+3x-x+1}{x\left(x-1\right)\left(x+1\right)}=\frac{x^2+2x+1}{x\left(x-1\right)\left(x+1\right)}=\frac{\left(x+1\right)^2}{x\left(x-1\right)\left(x+1\right)}\)
\(=\frac{x+1}{x\left(x-1\right)}\)
\(\frac{4x+1}{2}-\frac{3x+2}{3}\)
\(=\frac{12x+3}{6}-\frac{6x+4}{6}=\frac{6x-1}{6}\)
tương tự đến hết nha a hay cj gì đps !
a) \(\frac{4.x+1}{2}-\frac{3.x+2}{3}=\frac{3.\left(4.x+1\right)-2.\left(3.x+2\right)}{6}\)
\(=\frac{12.x+3-6.x-4}{6}\)
\(=\frac{6.x-1}{6}\)
b)\(\frac{x+3}{x^2-1}-\frac{1}{x^2+x}\)
\(=\frac{x+3}{\left(x-1\right).\left(x+1\right)}-\frac{1}{x.\left(x+1\right)}\)
\(=\frac{x.\left(x+3\right)-\left(x-1\right)}{x.\left(x-1\right).\left(x+1\right)}\)
\(=\frac{x^2+3.x-x+1}{x.\left(x-1\right).\left(x+1\right)}\)
\(=\frac{x^2+2.x+1}{x.\left(x-1\right).\left(x+1\right)}\)
\(=\frac{\left(x+1\right)^2}{x.\left(x-1\right).\left(x+1\right)}\)
\(=\frac{x+1}{x.\left(x-1\right)}\)
\(=\frac{x+1}{x^2-x}\)
c)\(\frac{3}{2.x^2+2.x}+\frac{2.x-1}{x^2-1}-\frac{1}{2}\)
\(=\frac{3}{2.x.\left(x+1\right)}+\frac{2.x-1}{\left(x-1\right).\left(x+1\right)}-\frac{1}{2}\)
\(=\frac{3.\left(x-1\right)+2.x.\left(2.x-1\right)-x.\left(x-1\right).\left(x+1\right)}{2.x.\left(x-1\right).\left(x+1\right)}\)
\(=\frac{3.x-3+4.x^2-2.x-x.\left(x^2-1\right)}{2.x.\left(x-1\right).\left(x+1\right)}\)
\(=\frac{3.x-3+4.x^2-2.x-x^3+x}{2.x.\left(x-1\right).\left(x+1\right)}\)
\(=\frac{2.x-3+4.x^2-x^3}{2.x.\left(x-1\right).\left(x+1\right)}\)
\(=\frac{-x^3+4.x^2+2.x-3}{2.x.\left(x-1\right).\left(x+1\right)}\)
\(=\frac{-x^3-x^2+5.x^2+5.x-3.x-3}{2.x.\left(x-1\right).\left(x+1\right)}\)
\(=\frac{-x^2.\left(x+1\right)+5.x.\left(x+1\right)-3.\left(x+1\right)}{2.x.\left(x-1\right).\left(x+1\right)}\)
\(=\frac{-\left(x+1\right).\left(x^2-5.x+3\right)}{2.x.\left(x-1\right).\left(x+1\right)}\)
\(=\frac{-\left(x^2-5.x+3\right)}{2.x.\left(x-1\right)}\)
\(=-\frac{x^2-5.x+3}{2.x^2-2.x}\)
Tính
a, \(\frac{1}{\left(y-1\right)\left(y-2\right)}+\frac{2}{\left(2-y\right)\left(3y-y\right)}+\frac{3}{\left(1-y\right)\left(y-3\right)}\)
b, \(\frac{x^2}{x+1}+\frac{2x}{x^2-1}-\frac{1}{1-x}+1\)
c, \(\frac{1}{x^2+3x+2}-\frac{2x}{x^2+4x^2+4x}+\frac{1}{x^2+5x+6}\)
Tính
a) \(\frac{x^3+1}{x}.\left(\frac{1}{x+1}+\frac{x-1}{x^2-x+1}\right)\)
b) \(\frac{x^3-3x^2+2x}{3x^2-4x+1}.\left(\frac{x-1}{x}-\frac{2x-6}{x-1}+\frac{x+1}{x-2}\right)\)
c) \(\frac{3x-3y}{2x^2-2xy+2y^2}:\frac{6x^2-12xy+6y^2}{5x^3+5y^3}:\frac{5x}{x-y}\)
a)\(ĐKXĐ:x\ne0;-1\)
Ta có:\(\frac{x^3+1}{x}.\left(\frac{1}{x+1}+\frac{x-1}{x^2-x+1}\right)=\frac{x^3+1}{x}.\frac{\left(x^2-x+1\right)+\left(x+1\right)\left(x-1\right)}{\left(x+1\right)\left(x^2-x+1\right)}\)
\(=\frac{x^3+1}{x}.\frac{x^2-x+1+\left(x^2-1\right)}{x^3+1}=\frac{2x^2-x}{x}=\frac{2x\left(x-1\right)}{x}=2\left(x-1\right)\)
Giải phương trình \(\left(\frac{7}{x^2+x-12}-\frac{1}{x^2-3x+2}-\frac{1}{x^2-5x+6}-\frac{3}{x^2+5x+4}\right)=\frac{3x}{x^2-1}\)
bài 1 : thực hiện các phép tính
a. \(\frac{4x-1}{3x^2y}-\frac{7x-1}{3x^2y}\)
b.\(\frac{4x+1}{2}-\frac{3x+2}{3}\)
c.\(\frac{5x^2-y^2}{xy}-\frac{3x-2y}{y}\)
d.\(\frac{3x}{5x+5y}-\frac{x}{10x-10y}\)
e.\(\frac{x+3}{x}-\frac{x}{x-3}+\frac{9}{x^2-3x}\)
f.\(\frac{x+3}{x^2-1}-\frac{1}{x^2+x}\)
g.\(\frac{1}{3x-2}-\frac{4}{3x+2}-\frac{-10x+8}{9x^2-4}\)
h.\(\frac{x+9y}{x^2-9y^2}-\frac{3y}{x^2+3xy}\)
i.\(\frac{3}{2x+6}-\frac{x-6}{2x^2+6x}\)
bài 1: Thực hiện các phép tính
a.\(\frac{4x-1}{3x^2y}-\frac{7x-2}{3x^2y}\)
b.\(\frac{4x+1}{2}-\frac{3x+2}{3}\)
c.\(\frac{5x^2-y^2}{xy}-\frac{3x-2y}{y}\)
d.\(\frac{3x}{5x+5y}-\frac{x}{10x-10y}\)
e. \(\frac{x+3}{x}-\frac{x}{x-3}+\frac{9}{x^2-3x}\)
f..\(\frac{x+3}{x^2-1}-\frac{1}{x^2+x}\)
g. \(\frac{1}{3x-2}-\frac{4}{3x+2}-\frac{-10x+8}{9x^2-4}\)
h.\(\frac{x+9y}{x^2-9y^2}-\frac{3y}{x^2+3xy}\)
i.\(\frac{3}{2x+6}-\frac{x-6}{2x^2+6x}\)
8,Thực hiện phép tính
a,\(\frac{5x^2-y^2}{xy}-\frac{3x-2y}{y}\)
b,\(\frac{3}{2x+6}-\frac{x-6}{2x^2+6x}\)
c,\(\frac{2x}{x^2+2xy}+\frac{y}{xy-2y^2}+\frac{4}{x^2-4y^2}\)
d,\(\frac{1}{x-y}+\frac{3xy}{y^3-x^3}+\frac{x-y}{x^2+xy+y^2}\)
e,\(\frac{2x+y}{2x^2-xy}+\frac{16x}{y^2-4x^2}+\frac{2x-y}{2x^2+xy}\)
f,\(\frac{1}{1-x}+\frac{1}{1+x}+\frac{2}{1+x^2}+\frac{4}{1+x^4}+\frac{8}{1+x^8}+\frac{16}{1+x^{16}}\)