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Hãy luôn nhớ cảm ơn và vote 5*
nếu câu trả lời hữu ích nhé!
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214
Đáp án: $\dfrac{1}{1.2}+\dfrac{1}{3.4}+\dfrac{1}{5.6}+...+\dfrac{1}{49.50}=\dfrac{1}{26}+\dfrac{1}{27}+\dfrac{1}{28}+...+\dfrac{1}{50}$
Giải thích các bước giải:
Ta có: $\dfrac{1}{1.2}+\dfrac{1}{3.4}+\dfrac{1}{5.6}+...+\dfrac{1}{49.50}$
$=1-\dfrac{1}{2}+\dfrac{1}{3}-\dfrac{1}{4}+\dfrac{1}{5}-\dfrac{1}{6}+...+\dfrac{1}{49}-\dfrac{1}{50}$
$=\left ( 1+\dfrac{1}{3}+\dfrac{1}{5}+...+\dfrac{1}{49} \right )-\left ( \dfrac{1}{2}+\dfrac{1}{4}+\dfrac{1}{6}+...+\dfrac{1}{50} \right )$
$=\left ( 1+\dfrac{1}{3}+\dfrac{1}{5}+...+\dfrac{1}{49} \right )+\left ( \dfrac{1}{2}+\dfrac{1}{4}+\dfrac{1}{6}+...+\dfrac{1}{50} \right )-2\left ( \dfrac{1}{2}+\dfrac{1}{4}+\dfrac{1}{6}+...+\dfrac{1}{50} \right )$
$=\left ( 1+\dfrac{1}{2}+\dfrac{1}{3}+\dfrac{1}{4}+\dfrac{1}{5}+\dfrac{1}{6}+...+\dfrac{1}{49}+\dfrac{1}{50} \right )-\left ( 1+\dfrac{1}{2}+\dfrac{1}{3}+...+\dfrac{1}{25} \right )$
$=\dfrac{1}{26}+\dfrac{1}{27}+\dfrac{1}{28}+...+\dfrac{1}{50}$
Vậy $\dfrac{1}{1.2}+\dfrac{1}{3.4}+\dfrac{1}{5.6}+...+\dfrac{1}{49.50}=\dfrac{1}{26}+\dfrac{1}{27}+\dfrac{1}{28}+...+\dfrac{1}{50}$
Hãy giúp mọi người biết câu trả lời này thế nào?
19
20
Đáp án:
1/1.2+1/3.4+1/5.6+...+1/49.50=1/26+1/27+1/28+...+1/50
= 1/1-1/2+1/3-1/4+...+1/50
= (1/1+1/3+...+1/49)-(1/2+1/4+...+1/50)
= (1/1+1/2+1/3+...+1/49+1/50)-2(1/2+1/4+...+1/50)
=1/1+1/2+1/3+...+1/49+1/50-1-1/2-1/3-...-1/25
=1/26+1/27+1/28+...+1/50
Vậy 1/1.2+1/3.4+1/5.6+...+1/49.50=1/26+1/27+1/28+...+1/50
MK TRÌNH BÀY HƠI KHÓ HIỂU MONG BN THÔNG CẢM
Hãy giúp mọi người biết câu trả lời này thế nào?
19
20
sao vote cho mk 1 sao vậy
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20
mk trình bày ko đc dễ hiểu cho lắm nhưng là công sức của mk lm tính ra cx phải đc 3-4 sao chứ
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20
thất vọng quá ik
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20
huhu:((
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3
Mk vote cho 5 sao nè
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20
cảm ơn bn nha
`1/1.2+1/3.4+1/5.6+...+1/49.50=1/26+1/27+1/28+...+1/50` `= 1/1-1/2+1/3-1/4+...+1/50` = (1/1+1/3+...+1/49)-(1/2+1/4+...+1/50) `= (1/1+1/2+1/3+...+1/49+1/50)-2(1/2+1/4+...+1/50)` `=1/1+1/2+1/3+...+1/49+1/50-1-1/2-1/3-...-1/25` `=1/26+1/27+1/28+...+1/50` Vậy`1/1.2+1/3.4+1/5.6+...+1/49.50=1/26+1/27+1/28+...+1/50` Rút gọn`1/1.2+1/3.4+1/5.6+...+1/49.50=1/26+1/27+1/28+...+1/50` `= 1/1-1/2+1/3-1/4+...+1/50` = (1/1+1/3+...+1/49)-(1/2+1/4+...+1/50) `= (1/1+1/2+1/3+...+1/49+1/50)-2(1/2+1/4+...+1/50)` `=1/1+1/2+1/3+...+1/49+1/50-1-1/2-1/3-...-1/25` `=1/26+1/27+1/28+...+1... xem thêm
`= (1/1+1/3+...+1/49)-(1/2+1/4+...+1/50)`
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