A= 1.1 + 2.2 +3.3 + 4.4 + ... +20.20
B= 1.2.2 + 2.3.3 + 3.4.4 + 19.20.20
C= 1.2 +3.4 + 5.6 + ... + 19.20
Nhờ các bạn giải giúp mình các bạn toán sau:
A = 1.2 + 3.4 + 5 .6 + ... + 49.50
B = 1.1 + 2.2 + 3.3 + ... + 49.49
C = 2.2 + 4.4 + 6.6 + ... + 48.48
D = 1.2.2 + 2.3.3 + ... + 49.50.50
E = 1.2.3 + 2.3.4 + ... + 48.49.50
B = 49.(49 + 1).(2 . 49 + 1) / 6 = 40425
C = 4.(12 + 22 + … + 242 ) = 4.24.(24 + 1)(2.24 + 1) / 6 = 19600
F=(1.1/1.2).(2.2/2.3)(3.3/3.4).(4.4/4.5)
bạn ghi rõ lại đề bài đi
Bài làm:
Ta có: \(F=\left(\frac{1.1}{1.2}\right).\left(\frac{2.2}{2.3}\right).\left(\frac{3.3}{3.4}\right)\left(\frac{4.4}{4.5}\right)\)
\(F=\frac{1}{2}.\frac{2}{3}.\frac{3}{4}.\frac{4}{5}\)
\(F=\frac{1}{5}\)
Bài làm
\(F=\left(\frac{1.1}{1.2}\right)\left(\frac{2.2}{2.3}\right)\left(\frac{3.3}{3.4}\right)\left(\frac{4.4}{4.5}\right)\)
\(=\frac{1}{2}.\frac{2}{3}.\frac{3}{4}.\frac{4}{5}=\frac{1.2.3.4}{2.3.4.5}=\frac{1}{5}\)
a) A = 1.2.3 +2.3.3 +3.4.3 + 4.5.3 +...+98.99.3
b) B = 1.1 + 2.2 + 3.3 + 4.4 +...+98.98
A=1.2+2.3+3.4+4.5+...1999.2000
B=1.1+2.2+3.3+4.4+....1999.1999
C=1.2.3+2.3.4+3.4.5+....+48.49.50
Tính nhanh:
A=1.2+2.3+3.4+4.5+...1999.2000
B=1.1+2.2+3.3+4.4+....1999.1999
C=1.2.3+2.3.4+3.4.5+....+48.49.50
A= 1^2/1.2.2^2/2.3.3^2/3.4.4^2/4.5.5^2/5.6
B= 2^2/1.3.3^2/2.4.4^2/3.5.5^2/4.6
Giup minh nhe minh tick cho
A=12/1.2 . 22/2.3 . 32/3.4 . 42/4.5 . 52/5.6
⇒1.1/1.2 . 2.2/2.3 . 3.3/3.4 . 4.4/4.5 . 5.5/5.6
⇒1.2.3.4.5/1.2.3.4.5 . 1.2.3.4.5/2.3.4.5.6
⇒1 . 1/6 =1/6.
Vậy A=1/6
B=22/1.3 . 32/2.4 . 42/3.5 . 52/4.6
⇒2.2/1.3 . 3.3/2.4 . 4.4/3.5 . 5.5/4.6
⇒2.2.3.3.4.4.5.5/1.3.2.4.3.5.4.6 =48.
Vậy B=48.
E= 1.2.2+ 2.3.3+ 3.4.4+......+ 49.50.50
E= 1.2.2+2.3.3+3.4.4+.......+ 49.50.50
tính tổng C=1.2+2.3+3.4+...+98.99
rồi sử dụng kết quả tính tổng
a, S=1.99+2.98+3.97+4.96+...97.3+98.2+99.1
b, H=1.1+2.2+3.3+4.4+...+97.97+98.98
Ô tô đi với vận tốc 50km/giờ vì :
100 : 2 = 50
đs : 50
Ta có: C = 1.2 + 2.3 + 3.4 + ..... + 98.99
=> 3C = 3.(1.2 + 2.3 + 3.4 + ..... + 98.99)
=> 3C = 1.2.(3 - 0) + 2.3.(4 - 1) + .... + 98.99.(100 - 97)
=> 3C = 1.2.3 - 1.2.3 + 2.3.4 - 2.3.4 + ..... + 98.99.100
=> 3C = 98.99.100
=> C = $C=\frac{98.99.100}{3}=485100$
Trả lời hộ mình câu h= 1.1+2.2+ 3.3+4.4+...+98.98