Cho T= 1/2+5/6+11/15+...+2351/2352+2448/2450+49/50 Tính T.
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\(=>S=\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{48.49}+\frac{1}{49.50}\)
\(=>S=\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+..+\frac{1}{48}-\frac{1}{49}+\frac{1}{49}-\frac{1}{50}=\frac{1}{1}-\frac{1}{50}=\frac{49}{50}\)
vậy S=49/50
1/2+1/6+1/12+1/20+.....+1/2352+1/2450
=1/1.2+1/2.3+1/3.4+1/4.5+.....+1/48.49+1/49.50
=1-/2+1/2-1/31/3-1/4+1/4-1/5+.....+1/48-1/49+1/49-1/50
=1-1/50
=49/50
\(\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+...+\frac{1}{2352}+\frac{1}{2450}\\ \)
\(=\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+...+\frac{1}{49.50}\)
\(=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+....+\frac{1}{49}-\frac{1}{50}\)
\(=1-\frac{1}{50}\)
\(=\frac{49}{50}\)
S=1/2+1/6+...............+1/2450
S=1/1.2+1/2.3+............+1/49.50
S=1-1/2+1/2-1/3+..........+1/49-1/50
S=1-1/50
S=49/50
S=1/2+1/6+...............+1/2450
S=1/1.2+1/2.3+............+1/49.50
S=1-1/2+1/2-1/3+..........+1/49-1/50
S=1-1/50
S=49/50
a, [1 - 2 ]+[ 3 - 4] +[5 - 6.]..+ [49 - 50] có 25 số hạng
=-1+[-1]+[-1]+...+[-1]
=-1.25
=-25
vậy b=-25
12+1 + 22+2 + 32+3 + 42+4 + ... + 482+48 + 492+49 + 502+50
= (1+2+3+4+..+48+49+50) +(12+22+32+42+...+482+492+502)
Đến đay bạn tự tính nha
câu 2:
\(\frac{1}{2}+\frac{1}{6}+...+\frac{1}{2450}\)
\(=\frac{1}{1.2}+\frac{1}{2.3}+...+\frac{1}{49.50}\)
\(=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{49}-\frac{1}{50}\)
\(=1-\frac{1}{50}\)
\(=\frac{49}{50}\)
\(\frac{5}{11}.\frac{7}{25}+\frac{15}{11}.\frac{1}{5}\)
\(=\frac{5}{11}.\frac{7}{25}+\frac{5}{11}.3.\frac{1}{5}\)
\(=\frac{5}{11}.\frac{7}{25}+\frac{5}{11}.\frac{3}{5}\)
\(=\frac{5}{11}\left(\frac{7}{25}+\frac{3}{5}\right)\)
\(=\frac{5}{11}\left(\frac{7}{25}+\frac{15}{25}\right)\)
\(=\frac{5}{11}.\frac{22}{25}=\frac{2}{5}\)