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bài này hơi khó
\(\frac{\left[\left(e-m\right)^2-\left(e+m\right)^2\right]\left[\left(y-1\right)^2\left(y+1\right)^2\right]}{a.16.nh}.\frac{ê}{\frac{1}{u}}\)
\(=\frac{\left[\left(e-m\right)^2\left(e+m\right)^2\right]\left[\left(y-1\right)^2\left(y+1\right)^2\right]}{16.anh}.\frac{êu}{1}\)
\(=\frac{\left(e^2-2em+m^2-e^2-2em-m^2\right)\left(y^2-2y+1-y^2-2y-1\right)}{16.anh}\)
\(=\frac{-4em\left(-4y\right)}{16.anh}.êu\)
\(=\frac{emy}{anh}.êu\)
\(=\frac{em.yêu}{anh}\)
1, =\(\frac{2\left(\frac{1}{5}+\frac{1}{7}-\frac{1}{9}-\frac{1}{11}\right)}{4\left(\frac{1}{5}+\frac{1}{7}-\frac{1}{9}-\frac{1}{11}\right)}=\frac{1}{2}\)
2, A=\(\frac{1}{2}\cdot\frac{2}{3}\cdot\frac{3}{4}\cdot...\cdot\frac{99}{100}\)
= \(\frac{1\cdot2\cdot3\cdot....\cdot99}{2\cdot3\cdot4\cdot...\cdot100}=\frac{1}{100}\)
Vậy ......
hok tốt
\(B=\left(1-\frac{1}{2}\right)\left(1-\frac{1}{3}\right)\left(1-\frac{1}{4}\right)\)
\(=>B=\frac{1}{2}\cdot\frac{2}{3}\cdot\frac{3}{4}=\frac{1\cdot2\cdot3}{2\cdot3\cdot4}=\frac{1}{4}\)
Ta có công thức : với n thuộc N* thì ta luôn có :
\(1+\frac{1}{n\left(n+2\right)}=\frac{n\left(n+2\right)+1}{n\left(n+2\right)}=\frac{n^2+2n+1}{n\left(n+2\right)}=\frac{\left(n+1\right)^2}{n\left(n+2\right)}\)
Áp dụng vào bài toán ta được :
\(P=\left(1+\frac{1}{1.3}\right)\left(1+\frac{1}{2.4}\right).....\left(1+\frac{1}{49.51}\right)+\frac{2}{51}\)
\(=\frac{2^2}{1.3}.\frac{3^2}{2.4}.\frac{4^2}{3.5}.......\frac{50^2}{49.51}+\frac{2}{51}\)
\(=\frac{\left(2.3.4...50\right)\left(2.3.4...50\right)}{\left(1.2.3...49\right)\left(3.4.5....51\right)}+\frac{2}{51}\)
\(=\frac{50.2}{51}+\frac{2}{51}=\frac{102}{51}=2\)
\(A=1+\frac{1}{2}.\left(1+2\right)+\frac{1}{3}.\left(1+2+3\right)+...+\frac{1}{16}.\left(1+2+...+16\right)\)
\(=1+\frac{1}{2}.2.3:2+\frac{1}{3}.3.4:2+...+\frac{1}{16}.16.17:2=1+\frac{3}{2}+\frac{4}{2}+...+\frac{17}{2}=\frac{2+3+4+...+17}{2}=\frac{152}{2}=76\)
\(=\frac{\left(e^2-2em+m^2-e^2-2em-m^2\right)\left(y^2-2y+1-y^2-2y-1\right)}{a.16.n.h}\)\(\times\frac{ê}{u^{-1}}\)
= \(\frac{\left(-4\right)em.\left(-4\right)y}{a.16.n.h}\)\(\times\frac{ê}{u^{-1}}\)
= \(\frac{16.e.m.y}{16.a.n.h}\times\frac{ê}{u^{-1}}\)
= \(\frac{e.m.y}{a.n.h}\times\frac{ê}{\frac{1}{u}}\)
= \(\frac{e.m.y}{a.n.h}\timesê.u\)
= \(\frac{e.m.y.ê.u}{a.n.h}\)
Biểu thức tình yêu hay đấy!!!