Biết \(1^4+2^4+3^4....+10^4=25333\).
Tính nhanh: \(2^4+4^4+6^4+...+20^4\)
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S = 2^4.(1^4+2^4+3^4+.....+10^4)
= 16 . 25333
= 405328
Tk mk nha
\(A=2^4+4^4+6^4+...+18^4+20^4\)
\(=2^4\left(1^4+2^4+3^4+...+9^4+10^4\right)\)
\(=16.25333=405328\)
`1/2+2/4+3/6+4/8+5/10+6/12`
`=1/2+1/2+1/2+1/2+1/2+1/2`
`=1/2*6=3`
`1/3+1/4+1/5+8/10+20/15+20/30`
`=(1/3+1/4)+(1/5+4/5)+(4/3+2/3)`
`=7/12+1+2`
`=7/12+3=43/12`
\(\dfrac{1}{2}+\dfrac{2}{4}+\dfrac{3}{6}+\dfrac{4}{8}+\dfrac{5}{10}+\dfrac{6}{12}\)
\(=\dfrac{1}{2}+\dfrac{1}{2}+\dfrac{1}{2}+\dfrac{1}{2}+\dfrac{1}{2}+\dfrac{1}{2}\)
\(=\dfrac{1}{2}\times6=3\)
\(------\)
\(\dfrac{1}{3}+\dfrac{1}{4}+\dfrac{1}{5}+\dfrac{8}{10}+\dfrac{20}{15}+\dfrac{20}{30}\)
\(=\dfrac{1}{3}+\dfrac{1}{4}+\dfrac{1}{5}+\dfrac{4}{5}+\dfrac{4}{3}+\dfrac{2}{3}\)
\(=\left(\dfrac{1}{3}+\dfrac{4}{3}+\dfrac{2}{3}\right)+\left(\dfrac{1}{5}+\dfrac{4}{5}\right)+\dfrac{1}{4}\)
\(=\dfrac{7}{3}+1+\dfrac{1}{4}\)
\(=\dfrac{28}{12}+\dfrac{12}{12}+\dfrac{3}{12}\)
\(=\dfrac{43}{12}\)
Bài 1:
A = 1 + 3 + 32 + ... + 3100
=> 3A = 3 + 32 + ... + 3101
=> 2A = 3101 - 1
=> A = \(\frac{3^{101}-1}{2}\)
B = 1 + 42 + 44 + ... + 4100
=> 8B = 42 + 44 + ... + 4102
=> 7B = 4102 - 1
=> B = \(\frac{4^{102}-1}{7}\)
Bài 2:
a) S1 = 22 + 42 + ... + 202
=> S1 = 22(1+22+...+102)
=> S1 = 22.385
=> S1 = 1540
b) S2 = 1002 + 2002 + ... + 10002
=> S2 = 1002(1+22+...+102)
=> S2 = 1002.385
=> S2 = 3850000
(10+20)+(2+8)+(4+6)=30+10+10
=50
1/3+1/6+4/3+2/6+2/3+5/6
=(1/3+4/3+2/3)+(1/6+2/6+5/6)
=7/3+8/6=7/3+4/3=11/3
Chuyển 14 thành 1. Và coi ... là x. Vậy:
\(1^4+1^4+x+9^4+10^4=\)\(25333\)
\(1+1+x+9^4+10^4=25333\)
\(\left(1+1\right)+x+9^4+10^4=\)\(25333\)
\(2+x+6561+10000=\)\(25333\)
\(x+\left(2+6561+10000\right)=\)\(25333\)
\(x+16563=25333\)
\(x=25333-16563\)
\(x=8770\)
Vậy số cần điền vào chỗ trống là 8770.
Học tốt nha.
cảm ơn bạn .ai đây ạ ........................................................................................................................................................................................ạ..........................
\(2^2+4^2+6^2+...+20^2\)
=\(\left(1.2\right)^4+\left(2.2\right)^4+\left(3.2\right)^4+...+\left(2.10\right)^4\)
=\(1^4.2^4+2^4.2^4+3^4.2^{\text{4}}+....+10^4.2^4\)
=\(2^4.\left(1^4+2^4+3^4+...+10^4\right)\)
=16.25333=405328