\(A=\dfrac{1}{6}+\dfrac{1}{12}+\dfrac{1}{20}+...+\dfrac{1}{420}\\ \Rightarrow A=\dfrac{1}{2\times3}+\dfrac{1}{3\times4}+...+\dfrac{1}{20\times21}\\ \Rightarrow A=\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+...+\dfrac{1}{20}-\dfrac{1}{21}\\\Rightarrow A=\dfrac{1}{2}-\dfrac{1}{20}=\dfrac{9}{20}\)
1/4+1/3xX=1/2
mn lm nhanh giúp mik vs
3/4xX-1=1/2xX
mn lm nhanh giúp mik vs
D=1/1.5+1/5.9+...+1/41.45 Mn lm nhanh giúp mik vs ạ
tính tổng sau
1/2+1/6+1/12+1/20+1/30+1/42+1/56
giải giúp mik vs
Tính tổng sau : \(\dfrac{1}{2}+\dfrac{1}{6}+\dfrac{1}{12}+\dfrac{1}{20}+\dfrac{1}{30}+\dfrac{1}{42}+\dfrac{1}{56}\)
giúp mik nha, nhớ lm cả lời giải nx nhe. THANK YOU!!!!❤
tính:
1/2+1/3+1/6+1/12+1/16+1/20+1/30+1/35+1/42
giúp mik vs nha !!!
3xX+X=20
mn lm nhanh giúp mik vs
Tính nhanh:
a)1/2+5/6+11/12+19/20+29/30+41/42+55/56+71/72+89/90
b)4/3.7+4/7.11+4/11.15+4/15.19+4/19.23+4/23.27
c)1/10+1/40+1/88+1/154+1/138+1/340
Các bạn giúp mik vs,làm ơn.ai nhanh mik tick cho.thank you very much
1/2 + 1/6 + 1/12 + 1/20 + ...... + 1/420 + 1/462
Ai trả lời nhanh nhất mk tk