Rút gọn phân thức M\(=\frac{x^2+x+1}{7x^3-7}\)
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MU
3
5 tháng 7 2019
\(\frac{1}{3-\sqrt{7}}-\frac{1}{3+\sqrt{7}}\)
\(=\frac{3+\sqrt{7}}{\left(3-\sqrt{7}\right)\left(3+\sqrt{7}\right)}-\frac{3-\sqrt{7}}{\left(3+\sqrt{7}\right)\left(3-\sqrt{7}\right)}\)
\(=\frac{3+\sqrt{7}-3+\sqrt{7}}{9-7}\)
\(=\frac{2\sqrt{7}}{2}\)
\(=\sqrt{7}\)
phần B là gì cơ?
DL
1
10 tháng 1 2020
A=\(\frac{x^3-7x+6}{x^3+5x^2-2x-24}\)=\(\frac{x^3-2x^2+2x^2-4x-3x+6}{x^3-2x^2+7x^2-14x+12x-24}\)=\(\frac{x^2\left(x-2\right)+2x\left(x-2\right)-3\left(x-2\right)}{x^2\left(x-2\right)+7x\left(x-2\right)+12\left(x-2\right)}\)=\(\frac{\left(x-2\right)\left(x^2+2x-3\right)}{\left(x-2\right)\left(x^2+7x+12^{^{^{^{^{^{^{^{^{ }}}}}}}}}\right)}\)=\(\frac{\left(x-2\right)\left(x^2-x+3x-3\right)}{\left(x-2\right)\left(x^2+3x+4x+12\right)}\)=\(\frac{\left(x-2\right)\left(x-1\right)\left(x+3\right)}{\left(x-2\right)\left(x+4\right)\left(x+3\right)}\)=\(\frac{x-1}{x+4}\)
AX
0
BT
1 tháng 12 2017
a/ \(\frac{7x-14y}{x^2-4y^2}=\frac{7\left(x-2y\right)}{x^2-\left(2y\right)^2}=\frac{7\left(x-2y\right)}{\left(x-2y\right)\left(x+2y\right)}=\frac{7}{x+2y}.\)
b/ \(\frac{1-\frac{2y}{x}+\frac{y^2}{x^2}}{\frac{1}{x}-\frac{1}{y}}=\frac{\frac{x^2-2xy+y^2}{x^2}}{\frac{y-x}{xy}}=\frac{\left(x-y\right)^2}{x^2}.\frac{xy}{-\left(x-y\right)}=-\frac{y\left(x-y\right)}{x}=\frac{y\left(y-x\right)}{x}\)
26 tháng 11 2017
M = 1/(x+1).(x+2) + 1/(x+2).(x+3) + 1/(x+3).(x+4) + 1/(x+4).(x+5) + 1/x+5
= 1/x+1 - 1/x+2 + 1/x+2 - 1/x+3 + 1/x+3 - 1/x+4 + 1/x+4 - 1/x+5 + 1/x+5 = 1/x+1
k mk nha
RZ
13 tháng 9 2016
\(\frac{x^2+5x+6}{x^2+7x+12}\)=\(\frac{x^2+2x+3x+6}{x^2+3x+4x+12}\)=\(\frac{x\left(x+2\right)+3\left(x+2\right)}{x\left(x+3\right)+4\left(x+3\right)}\)=\(\frac{\left(x+3\right)\left(x+2\right)}{\left(x+4\right)\left(x+3\right)}\)=\(\frac{x+2}{x+4}\)
BC
1
14 tháng 12 2020
ĐKXĐ: \(x\ne1;x\ne-\dfrac{3}{2}\)
Ta có: \(\dfrac{3x^3-7x^2+5x-1}{2x^3-x^2-4x+3}=\dfrac{\left(x-1\right)^2\left(3x-1\right)}{\left(x-1\right)^2\left(2x+3\right)}=\dfrac{3x-1}{2x+3}\)
VT
3
KB
15 tháng 12 2017
\(M=\frac{x^8\left(x+1\right)+x^6\left(x+1\right)+x^4\left(x+1\right)+x^2\left(x+1\right)+x+1}{\left(x-1\right)\left(x+1\right)}\)
\(=\frac{\left(x^8+x^6+x^4+x^2+1\right)\left(x+1\right)}{\left(x-1\right)\left(x+1\right)}\)
\(=\frac{x^8+x^6+x^4+x^2+1}{x-1}\)
NH
15 tháng 12 2017
M=\(\frac{\left(x^9+x^8\right)\left(x^7+x^6\right)+...+\left(x+1\right)}{\left(x+1\right)\left(x-1\right)}\)
M=\(\frac{x^8\left(x+1\right)+x^6\left(x+1\right)+...+\left(x+1\right)}{\left(x+1\right)\left(x-1\right)}\)
M=\(\frac{\left(x+1\right)\left(x^8+x^6+x^4+x^2\right)}{\left(x+1\right)\left(x-1\right)}\)
M=\(\frac{x^8+x^6+x^4+x^2}{x-1}\)
m=\(m=\frac{^{x^2^{ }}+x+1}{7\left(x^3-1\right)}=\frac{x^2+x+1}{7\left(x-1\right)\left(x^2+x+1\right)}=\frac{1}{7\left(x-1\right)}\)