rut gon 1+7^2+7^3+7^4+...+7^99
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rut gon : M = 1+7+7^2+7^3+7^4+...................................+7^100
\(7M=7+7^2+7^3+...+7^{101}\)
\(7M-M=\left(7+7^2+...+7^{101}\right)-\left(1+7+..+7^{100}\right)\)
\(6M=7^{101}-1\)
\(M=\frac{7^{101}-1}{6}\)
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rut gon bieu thuc (6x+7)(2x-3)-(4x+1)(3x-7/4)
rut gon 1 + 7 + 7^2 + ... +7^101
Đặt A = 1 + 7 + 72+...+7101
=> 7A = 7 + 72+73+...+7102
=> 7A-A= 7102-1
6A = 7102-1
\(\Rightarrow A=\frac{7^{102}-1}{6}\)
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rut gon
x^7+x^6+x^5+x^4+x^3+x^2+x+1/x^2-1
rut gon A=1+1^ 2+1^ 3+1^4+1^5+1^6+1^7+1^8+1^9+...+1^2012
1) Rut gon bieu thuc A = \(\left(4+\sqrt{7}\right).\left(\sqrt{2}-\sqrt{14}\right).\sqrt{4-\sqrt{7}}\)
rut gon 1*2*5+3*3*15+4*8*20+7*14*350/2*5*11+6*10+33+8*20*44+14*35*770
rut gon P= 1+-3+5+-7+...+17+-19
P=1+(-3)+5+(-7)+...17+(-19)
P=(-2)+(-2)+...+(-2)
P=(-2). 9,5 ( vì có 9,5 số -2)
P= -19
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rut gon bieu thuc :5/11*5/7+5/11*2/7+6/11
=\(\dfrac{5}{11}\left(\dfrac{5}{7}+\dfrac{2}{7}\right)+\dfrac{6}{11}\)
=\(\dfrac{5}{11}\times1+\dfrac{6}{11}\)
=\(\dfrac{11}{11}\)=1
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\(\dfrac{5}{11}\cdot\dfrac{5}{7}+\dfrac{5}{11}\cdot\dfrac{2}{7}+\dfrac{6}{11}=\dfrac{5}{11}\cdot\left(\dfrac{5}{7}+\dfrac{2}{7}\right)+\dfrac{6}{11}=\dfrac{5}{11}\cdot1+\dfrac{6}{11}=\dfrac{5}{11}+\dfrac{6}{11}=1\)
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