\(B=1+\dfrac{1}{2}\left(1+2\right)+\dfrac{1}{3}\left(1+2+3\right)+...+\dfrac{1}{20}\left(1+2+...+20\right)\)
\(B=1+\dfrac{1}{2}.2.3:2+\dfrac{1}{3}.3.4:2+...+\dfrac{1}{20}.20.21:2\)
\(B=\dfrac{2}{2}+\dfrac{3}{2}+...+\dfrac{21}{2}\)
\(B=\dfrac{2+3+...+21}{2}\)
\(B=\dfrac{230}{2}\)
\(\Rightarrow B=115\)
giá trị lớn nhất
B=1+\(\dfrac{1}{2}\)(1+2)+\(\dfrac{1}{3}\)(1+2+3)+\(\dfrac{1}{4}\)(1+2+3+4)+......................+\(\dfrac{1}{20}\)(1+2+3+.............+20)
A=(2/1+2)+(2+3/1+2+3)+...+(2+3+4+...+20/1+2+3+4+...+20)
Giá trị biểu thức :
\(\dfrac{1}{2}+\left(\dfrac{1}{2}\right)^2+\left(\dfrac{1}{2}\right)^3+\left(\dfrac{1}{2}\right)^4+....+\left(\dfrac{1}{2}\right)^{20}\) Là :
A \(\dfrac{2^{20}-1}{2^{20}}\) B.\(\dfrac{1}{2}-\dfrac{1}{2^{20}}\)
C . 1 D . \(\dfrac{2^{20}-2}{2^{20}}\)
- Ghi cách giải nữa nha!
Cho đa thức:
f(x)=a.x^2009-b.x^2011+1+1/2.(1+2)+1/3.(1+2+3)+1/4.(1+2+3+4)+...+1/20.(1+2+3+...+20).
Tính f(1) biết f(-1)=-1780
B = 1 + 5 + 52 + 53 + ....... + 52008 + 52009
S = 1 + 2 + 5 + 14 + ....... + 3n-1 + 1/2 (với n thuộc Z)
A = 1 + 3/2^3 + 4/2^4 + 5/2^5 + ...... + 100/2^100
Q = 1 + 1/2*(1+2) + 1/3*(1+2+3) + 1/4*(1+2+3+4) + ...... + 1/20*(1+2+3+.....+20)
M = -4/1*5 - 4/5*9 - 4/9*13 - ....... - 4/(n+4)*n
Giúp mk với! Mk đang cần gấp lắm !!!!!
Tính tổng
\(S=1+\frac{1}{2}\left(1+2\right)+\frac{1}{3}\left(1+2+3\right)+...+\frac{1}{20}\left(1+2+...+20\right)\)
a,\(\dfrac{8^{20}+4^{20}}{4^{25}+64^5}\)
b,\(\left(1+\dfrac{2}{3}-\dfrac{1}{4}\right).\left(\dfrac{4}{5}-\dfrac{3}{4}\right)^2\)
c,\(23\dfrac{1}{3}:\left(\dfrac{-5}{7}\right)-13\dfrac{1}{3}:\left(\dfrac{-5}{7}\right)\)
d,1:\(\left(\dfrac{2}{3}-\dfrac{3}{4}\right)^2\)
e,\(\dfrac{45^{10}.5^{20}}{75^{15}}\)
tính giá trị của biểu thức A=1/20-1/20*19-1/19*18-1/18*17-...1/3*2-1/2*1
