tính A=1^2+2^2+3^2+..+50^2
Tính
a, 2^2+4^2+6^2+...........+50^2
b, 1^3+2^3+3^3+............+50^3
Tính
1)A=1×2×3+2×3×4+.....+48×49×50
2)B=1×2+2×3+3×4+......+49×50
A = 1 × 2 × 3 + 2 × 3 × 4 + .....+ 48 × 49 × 50
ta có 4 x A = 1 x 2 x 3 x 4 + 2 x 3 x 4 x (5 -1) + .....+ 48 × 49 × 50 x (51 - 47)
= 1 x 2 x 3 x 4 + 2 x 3 x 4 x 5 - 1 x 2 x 3 x 4 + ... + 48 x 49 x 50 x 51 - 47 x 48 x 49 x 50
= 48 x 49 x 50 x 51
suy ra A = (48 x 49 x 50 x 51) : 4
= 12 x 49 x 50 x 51
nhớ k cho mik nha rùi mik lm nốt cho
A = 1 × 2 × 3 + 2 × 3 × 4 + .....+ 48 × 49 × 50
ta có 4 x A = 1 x 2 x 3 x 4 + 2 x 3 x 4 x (5 -1) + .....+ 48 × 49 × 50 x (51 - 47)
= 1 x 2 x 3 x 4 + 2 x 3 x 4 x 5 - 1 x 2 x 3 x 4 + ... + 48 x 49 x 50 x 51 - 47 x 48 x 49 x 50
= 48 x 49 x 50 x 51
suy ra A = (48 x 49 x 50 x 51) : 4
= 12 x 49 x 50 x 51
Tính A=1 +2+2^2+2^3+2^4+...+2^49+2^50
`#3107.101107`
\(A=1+2+2^2+2^3+...+2^{49}+2^{50}\)
\(2A=2+2^2+2^3+...+2^{50}+2^{51}\)
\(2A-A=\left(2+2^2+2^3+...+2^{51}\right)-\left(1+2+2^2+...+2^{50}\right)\)
\(A=2+2^2+2^3+...+2^{51}-1-2-2^2-...-2^{50}\)
\(A=2^{51}-1\)
Vậy, \(A=2^{51}-1.\)
a) Hãy tính : [-1/7];[3,7];[-4];[-43/10]
b) Cho x = 3,7. So sánh :
A = [x] + [x+1/5] + [x+2/5] + [x+3/5] + [x+4/5] và B = [5x]
c) Tính [100/3] + [100/32] + [100/33] + [100/34]
d) Tính [50/2] + [50/22] + [50/23] + [50/24] + [50/25]
Giúp mik nha
Toán HS giỏi đấy
Thank you
Tính A=1*50+2*49+3*48+...+49*2+50*1
=> A = 1 x 50 + 2 x ( 50 - 1 ) + 3 x ( 50 - 2 ) + .... + 49 x ( 50 - 48 ) + 50 x ( 50 - 49 )
= 1 x 50 + 2 x 50 - 1 x 2 + 3 x 50 - 2 x 3 + ..... + 49 x 50 - 48 x 49 + 50 x 50 - 49 x 50
= ( 1 + 2 + 3 + .... + 50 ) x 50 + ( 1 x 2 + 2x 3 + .... + 49 x 50 )
= \(\frac{50.\left(50+1\right)}{2}\times50+\frac{49.50.51}{3}\)
= 63750 + 41650
= 105400
Cho A =1+2+2^2+2^3+...+ 2^50. Tính A?
A=1+2+22+23+...+250
2A=2+22+23+...+250+251
2A-A=251-1
A=251-1
\(A=1+2+2^2+2^3+...+2^{50}\)50
\(2.A=2+2^2+2^3+2^4+....+2^{51}\)
\(2.A-A=\)\(2+2^2+2^3+2^4+....+2^{51}-1+2+2^2+2^3+...+2^{50}\)
\(A=2^{51}-1\)
Ta có : A = 1 + 2 + 22 + 23 + .... + 250
=> 2A = 2 + 22 + 23 + 24 + .... + 251
Lấy 2A trừ A theo vế ta có :
2A - A = (2 + 22 + 23 + 24 + .... + 251) - (1 + 2 + 22 + 23 + .... + 250)
A = 251 - 1
Vậy A = 251 - 1
Hãy tính A= 1+2+2^2+2^3+...+2^49-(2^50+3)=?
50^2 - 49^2 + 48^2 - 47^2 + ... + 2^2 +1^2
= (50 + 49)(50 - 49) + (48 + 47)(48 - 47) + ... + (4 + 3)(4 - 3) + 4 + 1
= 50 + 49 + 48 + 47 + ... + 4 + 3 + 5
= (50 + 3)*48/2 + 5
= 1277
nếu thế này thì đề nhìn đẹp mắt hơn (^_^)
50^2 - 49^2 + 48^2 - 47^2 + ... + 2^2 - 1^2
= (50 + 49)(50 - 49) + (48 + 47)(48 - 47) + ... + (2 + 1)(2 - 1)
= 50 + 49 + 48 + 47 + ... + 2 + 1
= (1 + 50)*50/2
= 1275 bạn
k mk nhé thanks
tính các tổng sau
A=1*2+2*3+3*4+4*5+5*6+6*7...+49*50
B=1*50+2*49+3*48+...+49*2+50*1
Cho A = 1+ 2+2^2+2^3 + ......+ 2^ 50
tính A
\(\Rightarrow2A=2+2^2+2^3+2^4+...+2^{51}.\)
\(\Rightarrow2A-A=A=\left(2+2^2+2^3+2^4+...+2^{51}\right)-\left(1+2^2+2^3+...+2^{50}\right)\)
\(A=2^{51}-1\)
\(A=1+2+2^2+2^3+....+2^{50}\)
\(\Rightarrow2A=2+2^2+2^3+2^4+...+2^{51}\)
\(\Rightarrow2A-A=(2+2^2+2^3+2^4+...+2^{51})\)_\((1+2^2+2^3+...+2^{50})\)
Hay \(A=2^{51}-1\)