Tính M
M=\(\left(12^2+14^2+16^2+18^2+20^2\right)-\left(1^2+3^2+5^2+7^2+9^2\right)\)\(9^{2\left(\right)}\)
Cho biết : \(1^2+2^2+3^2+...+10^2=385.\)Tính nhanh : \(\left(12^2+14^2+16^2+18^2+20^2\right)-\left(1^2+3^2+5^2+7^2+9^2\right)\)
Cho : \(1^2+2^2+3^2+.....+10^2=385\)
Tính S= \(\left(12^2+14^2+16^2+18^2+20^2\right)-\left(1^2+3^2+5^2+7^2+9^2\right)\)
Ta thấy : 2\(^2\)=4=4.1\(^2\)
4\(^2\)=16=4.2\(^2\)
6\(^2\)=36=4.3\(^2\)
...
20\(^2\)=400=4.10\(^2\)
=>S=2\(^2\)+4\(^2\)+6\(^2\)+...+20\(^2\)=4.(1\(^2\)+2\(^2\)+3\(^2\)+...+10\(^2\))
= 4.385
=1540
Vậy tổng S = 1540
Cho \(1^2+2^2+3^2+...+10^2=385\)
Tính nhanh S = \(\left(12^2+14^2+16^2+18^2+20^2\right)-\left(1^2+3^2+5^2+7^2+9^2\right)\)
1155 nhé bn nhưng mk k bt cách làm
Bn nào bt giúp mk vs
Cho biết \(1^2+2^2+3^2+....+10^2=365\)
Tính nhanh S= \(\left(12^2+14^2+16^2+18^2+20^2\right)-\left(1^2+3^2+5^2+7^2+9^2\right)\)
Cho biết \(1^2+2^2+3^2+...+10^2=385\).Tính nhanh : \(\left(12^2+14^2+16^2+18^2+20^2\right)-\left(1^2+3^2+5^5+7^2+9^2\right)\)
\(A=\left(12^2+14^2+16^2+18^2+20^2\right)-\left(1^2+3^2+5^2+7^2+9^2\right)\)
\(A=\left(12^2-1^2\right)+\left(14^2-3^2\right)+\left(16^2-5^2\right)+\left(18^2-7^2\right)+\left(20^2-9^2\right)\)\(A=\left(12+1\right)\left(12-1\right)+\left(14+3\right)\left(14-3\right)+\left(16-5\right)\left(16+5\right)+\left(18-7\right)\left(18+7\right)+\left(20-9\right)\left(20+9\right)\)
\(A=11.13+11.17+11.21+11.25+11.29\)
\(A=11.\left(13+17+21+25+29\right)\)
\(A=11.\left[\left(13+17\right)+\left(21+29\right)+25\right]\)
\(A=11.\left(30+50+25\right)\)
\(A=11.105=1155\)
Giup mình bài này với !
Cho biết \(1^2+2^2+3^2+4^2+5^2+6^2+7^2+8^2+9^2+10^2=385\) . Tính
A = \(2^2+4^2+6^2+8^2+...+18^2+20^2\)
B = \(\left(12^2+14^2+16^2+18^2+20^2\right)-\left(1^2+3^2+5^2+7^2+10^2\right)\)
Ta thấy A gấp 12+22+....+102 4 lần nên Tổng A gấp 4 lần nó
=> A=385.4=1540
Tính :
\(A=\left(12^2+14^2+...+20^2\right)-\left(1^2+3^2+5^2+7^2+9^2\right)\)
\(A=\left(12^2+14^2+...+20^2\right)-\left(1^2+3^2+5^2+7^2+9^2\right)\)
\(A=12^2+14^2+...+20^2-1^2+3^2+5^2+7^2+9^2\)
\(A=2^2.\left(6^2+7^2+8^2+9^2\right)-\left(1^2+3^2+5^2+7^2+9^2\right)\)
\(A=2^2.330-\left(1+9+25+49+81\right)\)
\(A=1320-165\)
\(A=1155\)
Vậy : \(A=1155\)
Biết : \(1^2+2^2+.......+10^2=385\)
Tìm S = \(\left(12^2+14^2+16^2+18^2+20^2\right)-\left(1^2+3^2+5^2+7^2+9^2\right)\)
(Giải chi tiết giúp mik nhé !!!! - thanks trước )
\(\left(12^2+14^2+16^2+18^2+20^2\right)-\left(1^2+3^2+5^2+7^2+9^2\right)\\\Rightarrow\left[\left(2^2.6^2\right)+\left(2^2.7^2\right)....+\left(2^2.10^2\right)\right]-\left(1^2+3^2+...+9^2\right)\\ \Rightarrow2^2.\left(6^2+7^2....+.10^2\right)-\left(1^2+3^2+5^2+7^2+9^2\right)\\ \Rightarrow4.330-165=1155\)
Tính:
\(a.\frac{8^5.\left(-5\right)^8+\left(-2\right)^5.10^9}{2^{16}.5^7+20^8}\)
\(b.\frac{\left(-0,25\right)^{-5}.9^4.\left(-2\right)^{-3}-2^{-2}.6^9}{2^9.3^6+6^6.40}\)
\(c.\frac{2^{12}.3^5-4^6.9^2}{\left(2^2.3\right)^6+8^4.3^5}-\frac{5^{10}.7^3-25^5.49^2}{\left(125.7\right)^3+5^9.14^3}\)