\(B=1+\frac{1}{2}\left(1+2\right)+\frac{1}{3}\left(1+2+3\right)+...+\frac{1}{12}\left(1+2+3+...+12\right)\)
\(B=1.\left(\frac{1.2}{2}\right)+\frac{1}{2}.\left(\frac{2.3}{2}\right)+\frac{1}{3}.\left(\frac{3.4}{2}\right)+....+\frac{1}{12}.\left(\frac{12.13}{2}\right)\)
\(B=\frac{2}{2}+\frac{3}{2}+\frac{4}{2}+....+\frac{13}{2}=\frac{2+3+4+....+13}{2}=\frac{90}{2}=45\)
Tính B=54-1/2(1+2)-1/3(1+2+3)-...-1/12(1+2+3+...+12)
M=54-1/2(1+2)-1/3(1+2+3)-1/4(1+2+3+4)-....-1/12(1+2+....+12)
bài 1: tính:
a,1/5-1/2+/-1/4/
b,/-1/4/-3+3/4
c,3/4- 1 2 trên 3 (hỗn số)+/-1 1 trên 6/-2
d,(11/12-15/3+1/12-1/3):2/3
tính:
1/2 x (1+2) - 1/3 x (1+2+3) - ... - 1/12 x (1+2+3+...+12)
a,(1/2-2/3)^2
b,2:(1/2-2/3)^2
c,0,25^3.8^3
d,(-12)^4.6^4
e, 2:(1/2-2/3)^2+0,25^3.8^3-(-12)^4.6^4
(mai em thi rồi ạ)
tính
B=\(\frac{1}{2}\left(1+2\right)+\frac{1}{3}\left(1+2+3\right)+...+\frac{1}{12}\left(1+2+3+...+12\right)\)
a) thực hiện phép tính
1/12+3/15+11/12+1/71-12/10
2/3-4×(1/2+3/4)
b)tìm x
3/2x-7/3=-1/4
3/4-(x+1/2)=1/4
|2x-1|-1/2=1/3
Giúp mik vs mik cảm ơn
A)7^8:[2^9-1^18]+7^8.[1^36-5^12]. B)[-0,75-1^4]:(-5)+1^15-(-1^5):(-3)
C)9^10-1^90-1^72-1^56-1^42-1^30-1^20-1^12-1^6-1^2 D)1+1^2.(1+2)+1^3.(1+2+3)+1^4.(1+2+3+4)+...+1^16.(1+2+3+4+...+16)
