1^1+1^2+1^3=
15 bạn nhanh nhất nha
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TL :
( 15 x 15 ) : 2 x ( 15 x 15 ) : 2 x ( 15 x 15 ) : 2 + ( 0 + 1 + 2 + 2 + 3 + 45 ) x 0
= 0
=> vì : tất cả số nào nhân vs 0 đều = 0
_HT_
Ta có: A = 1.2.3 + 2.3.4 + 3.4.5 + ... + 18.19.20
=> 4A = 4(1.2.3 + 2.3.4 + 3.4.5 + ... + 18.19.20)
=> 4A = 1.2.3.4 + 2.3.4.4 + 3.4.5.4 +...... +18.19.20.4
=> 4A = 1.2.3.4 + 2.3.4(5 - 1) + 3.4.5.(6 - 2) +..... +18.19.20.(21 - 17)
=> 4A = 1.2.3.4 + 2.3.4.5 - 2.3.4 + 3.4.5.6 - 2.3.4.5 + ..... + 17.18.19.20 - 17.18.19.20
=> 4A =18.19.20
=> 4A = 6840
=> A = 1710
Đặt A=1.2.3+2.3.4+3.4.5+4.5.6+...+18.19.20
4A=(1.2.3+2.3.4+3.4.5+4.5.6+...+18.19.20)4
4A=1.2.3(4-0)+2.3.4(5-1)+3.4.5(6-2)+4.5.6(7-3)+...+18.19.20.(21-17)
4A=1.2.3.4+2.3.4.5-1.2.3.4+3.4.5.6-2.3.4.5+4.5.6.7-3.4.5.6+...+ 18.19.20.21-17.18.19.20
=>A =18.19.20.21
=>A+18.19.20.21/4
=> A=35910
x x\(\frac{5}{8}\)= 15 -\(\frac{1}{2}\)
x x\(\frac{5}{8}\)=\(\frac{29}{2}\)
x =\(\frac{29}{2}\):\(\frac{5}{8}\)
x =\(\frac{116}{5}\)
Chúc bạn học tốt.
😁😁😁
\(x\times\frac{5}{8}=15-\frac{1}{2}\)
\(x\times\frac{5}{8}=14\)
\(x=14:\frac{5}{8}\)
\(x=\frac{112}{5}\)
a) \(0,5x-\frac{2}{3}x=\frac{7}{12}\)
\(\frac{1}{2}x-\frac{2}{3}x=\frac{7}{12}\)
\(\Rightarrow x\left(\frac{1}{2}-\frac{2}{3}\right)=\frac{7}{12}\)
\(x.\frac{-1}{6}=\frac{7}{12}\)
\(x=\frac{7}{12}:\frac{-1}{6}\)
\(x=\frac{-7}{2}\)
b) \(x:4\frac{1}{3}=-2,5\)
\(x:\frac{13}{3}=\frac{-5}{2}\)
\(x=\frac{-5}{2}.\frac{13}{3}\)
\(x=\frac{-65}{6}\)
c) \(5,5x=\frac{13}{15}=\frac{11}{2}x=\frac{13}{5}\)
\(x=\frac{13}{5}:\frac{11}{2}\)
\(x=\frac{26}{55}\)
d) \(\left(\frac{3x}{7}+1\right):\left(-4\right)=\frac{-1}{28}\)
\(\frac{3x}{7}+1=\frac{-1}{28}.\left(-4\right)\)
\(\frac{3x}{7}+1=\frac{1}{7}\)
\(\frac{3x}{7}=\frac{1}{7}-1\)
\(\frac{3x}{7}=\frac{-6}{7}\)
\(\frac{3x}{7}=\frac{-6}{7}\Rightarrow\frac{3.\left(-2\right)}{7}=\frac{-6}{7}\)
Vậy x = -2
\(0,5x-\frac{2}{3}x=\frac{7}{12}\)\(\)
\(\frac{1}{2}x-\frac{2}{3}x=\frac{7}{12}\)
\(x.\left(\frac{1}{2}-\frac{2}{3}\right)=\frac{7}{12}\)
\(A=\frac{1}{25.27}+\frac{1}{27.29}+...+\frac{1}{73.75}=\frac{1}{2}\left(\frac{1}{25}-\frac{1}{27}+\frac{1}{27}-\frac{1}{29}+...+\frac{1}{73}-\frac{1}{75}\right)\)
\(A=\frac{1}{2}\left(\frac{1}{25}-\frac{1}{75}\right)\\ A=\frac{1}{75}\)
\(B=\frac{15}{90.94}+\frac{15}{94.98}+...+\frac{15}{146+150}=\frac{1}{4}\left(\frac{15}{90}-\frac{15}{94}+\frac{15}{94}-\frac{15}{98}+...+\frac{15}{146}-\frac{15}{150}\right)\)
\(B=\frac{1}{4}\left(\frac{15}{90}-\frac{15}{150}\right)=\frac{1}{60}\)
1-1/2+1/2-1/3+1/3+1/4-1/4+1/5-1/5+1/6-1/6+1/7-1/7+1/8-1/8+1/9-1/9+1/10-(1-1/3+1/3-3/5+3/5-4/7+5/9-5/9+6/11-6/11-7/13)=1+1/10-1+7/13=83/130
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