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tử số = 2^10 . 3^8 - 2^10 . 3^9 = 2^10 . 3^8 . (1-3)
mẫu số = 2^10 . 3^8 + 3^8 . 2^10 . 5 = 2^10 . 3^8 . (1+5)
Đ/S: \(\frac{1-3}{1+5}\)=\(\frac{-1}{3}\)
\(S=2^2+4^2+.....+20^2\)
\(S=1^2.2^2+2^2.2^2+.......+10^2.2^2\)
\(S=2^2.\left(1^2+2^2+.....+10^2\right)\)
\(S=4.385=1540\) (đề bài)
Ta có : \(C=\frac{1}{2}+\left(-\frac{2}{3}\right)+\left(-\frac{2}{3}\right)^2+\left(-\frac{2}{3}\right)^3+......+\left(-\frac{2}{3}\right)^{2018}\)
\(\Rightarrow C=\frac{1}{2}-\left(\frac{2}{3}+\left(\frac{2}{3}\right)^2+\left(\frac{2}{3}\right)^3+.....+\left(\frac{2}{3}\right)^{2018}\right)\)
Đặt \(\Rightarrow A=\frac{2}{3}+\left(\frac{2}{3}\right)^2+\left(\frac{2}{3}\right)^3+.....+\left(\frac{2}{3}\right)^{2018}\)
\(\Rightarrow\frac{2}{3}A=\left(\frac{2}{3}\right)^2+\left(\frac{2}{3}\right)^3+\left(\frac{2}{3}\right)^4+.....+\left(\frac{2}{3}\right)^{2019}\)
\(\Rightarrow A-\frac{2}{3}A=\frac{2}{3}-\frac{2}{3}^{2019}\)
\(\Rightarrow\frac{1}{3}A=\frac{2}{3}-\left(\frac{2}{3}\right)^{2019}\)
=> A = \(\left(\frac{2}{3}-\left(\frac{2}{3}\right)^{2019}\right).3\)
=> A = 2 - \(\frac{2^{2019}}{3^{2018}}\)
S=22+42+...+202
=> 1/2 .S=12+22+...+102
=> 1/2 .S=385
=> S = 385 . 2
=> S = 770
Vì 12+22+32+...+102 = 385
Mà S = 22+42+62+...+202
= 22.(12+22+32+...+102) = 4.385 = 1540
Ta có: S=22+42+62+...+202
=(2.1)2+(2.2)2+(2.3)2+...+(2.10)2
=22.12+22.22+22.32+...+22.102
=22.(1+22+32+...+102)
Mà 12+22+32+...+102=385 nên:
S=22.385
=4.385
=1540
Vậy S=1540
\(S=\left(2.1\right)^2+\left(2.2\right)^2+\left(2.3\right)^2+....+\left(2.10\right)^2\)
\(\Rightarrow S=2^2.1^2+2^2.2^2+....+2^2.10^2\)
\(\Rightarrow S=2^2\left(1^2+2^3+3^2+.....+10^2\right)\)
Áp dụng giả thiết từ đề
\(\Rightarrow S=2^2.385\)
\(\Rightarrow S=4.384=1540\)
\(S=2^2+4^2+6^2+...+20^2\)
\(=1^2.4+2^2.4+3^2.4+...+10^2.4\)
\(=4.\left(1^2+2^2+3^2+...+10^2\right)\)
\(=4.385=1540\)
Ta có:
\(S=2^2+4^2+6^2+...+20^2\)
\(\Rightarrow S=\left(1.2\right)^2+\left(2.2\right)^2+\left(2.3\right)^2+...+\left(2.10\right)^2\)
\(\Rightarrow S=1^2.2^2+2^2.2^2+2^2.3^2+...+2^2.10^2\)
\(\Rightarrow S=\left(1^2+2^2+3^2+...+10^2\right).2^2\)
\(\Rightarrow S=385.4\)
\(\Rightarrow S=1540\)
S=22+42+...+102
=(1*2)2+(2*2)2+...+(2*10)2
=12*22+22*22+...+22*102
=22*(12+22+...+102)
=4*385
=1540
S = 2^2 + 4^2 + 6^2 + .. +20^2
S = 2^2 + 2^2.2^2 + 2^2.3^2 + ... + 2^2 . 10^2
S = 2^2 ( 1 + 2^2 + 3^2 + .. + 10^2)
S = 4 . 385
S = 1540
Ta có : 12 + 22 + 32 + ..... + 102 = 385
=> 22(12 + 22 + 32 + ..... + 102) = 22.385
=> 22 + 42 + 62 + ...... + 202 = 4.385
=> 22 + 42 + 62 + ...... + 202 = 1540
Vậy 22 + 42 + 62 + ...... + 202 = 1540
Ta có : 12+...+102=385
=> 22.(12+22+...+102)=385.22
=> 22+42+62+...+202=1540
Vậy S=1540