2/3 + 3/4 : 3 = ?
giúp mình nhanh với ạ mình cảm ơn
\(A=\frac{\left[\left(25-1\right):1+1\right]\left(25+1\right)}{2}=325.\)
\(B=\frac{\left[\left(51-3\right):2+1\right]\left(51+3\right)}{2}=675\)
\(C=\frac{\left[\left(81-1\right):4+1\right]\left(81+1\right)}{2}=861\)
CHO B = 1/3 + 2/32 + 3/33 +...+ 100/3100 CHỨNG MINH RẰNG B BÉ HƠN 3/4
GIÚP MÌNH NHANH NHANH VỚI NHA ! MÌNH CẦN GẤP Ạ ! XIN GỬI LỜI CẢM ƠN TỚI NHỮNG BẠN GIÚP MÌNH
Ta có:
\(A=\frac{1}{3}+\frac{2}{3^2}+\frac{3}{3^3}+\frac{4}{3^4}+...+\frac{100}{3^{100}}\)
\(\Rightarrow3A=1+\frac{2}{3}+\frac{3}{3^2}+\frac{4}{3^3}+...+\frac{100}{3^{99}}\)
\(\Rightarrow2A=1+\frac{1}{3}+\frac{1}{3^2}+\frac{1}{3^3}+\frac{1}{3^4}+...+\frac{1}{3^{99}}-\frac{100}{3^{100}}\)
\(\Rightarrow6A=3+1+\frac{1}{3}+\frac{1}{3^2}+\frac{1}{3^3}+\frac{1}{3^4}+...+\frac{1}{3^{98}}-\frac{100}{3^{99}}\)
\(\Rightarrow4A=3-\frac{101}{3^{99}}+\frac{100}{3^{100}}=3-\frac{203}{3^{100}}\)
\(\Rightarrow A=\frac{3-\frac{203}{3^{100}}}{4}=\frac{3}{4}-\frac{203}{3^{100}.4}< \frac{3}{4}\Rightarrowđpcm\)
Vậy \(A< \frac{3}{4}\)
Mn giúp mình với ạ!Mình cảm ơn!
3/2.(x-5/3)-4/5=x+1
\(\dfrac{3}{2}\)(\(x\) - \(\dfrac{5}{3}\)) - \(\dfrac{4}{5}\) = \(x\) + 1
\(\dfrac{3}{2}\) \(x\) - \(\dfrac{15}{6}\) - \(\dfrac{4}{5}\) = \(x\) + 1
\(\dfrac{3}{2}\)\(x\) - \(x\) = 1 + \(\dfrac{15}{6}\) + \(\dfrac{4}{5}\)
\(\dfrac{1}{2}\)\(x\) =\(\dfrac{43}{10}\)
\(x\) = \(\dfrac{43}{10}\) \(\times\) 2
\(x\) = \(\dfrac{43}{5}\)
\(\dfrac{3}{2}\left(x-\dfrac{5}{3}\right)-\dfrac{4}{5}=x+1\\ \Rightarrow\dfrac{3.\left(x-\dfrac{5}{3}\right)}{2}-\dfrac{4}{5}=x+1\\ \Rightarrow\dfrac{3x-5}{2}-\dfrac{4}{5}=x+1\Rightarrow\dfrac{5\left(3x-5\right)}{10}-\dfrac{8}{10}=x+1\\ \Rightarrow\dfrac{15x-33}{10}=x+1\\ \Rightarrow\dfrac{15x-33}{10}-x=x+1\\ \Rightarrow\dfrac{15x-33}{10}=x+1-x\\ \Rightarrow5x-33=10\\ \Rightarrow5x=10+33\\\Rightarrow5x=43\\ \Rightarrow x=\dfrac{43}{5} \)
\(\dfrac{3}{2}\times\left(x-\dfrac{5}{3}\right)-\dfrac{4}{5}=x+1\)
\(\Leftrightarrow\dfrac{3}{2}\times x-\dfrac{5}{2}-\dfrac{4}{5}=x+1\)
\(\Leftrightarrow\dfrac{3}{2}\times x-x=1+\dfrac{5}{2}+\dfrac{4}{5}\)
\(\Leftrightarrow\dfrac{1}{2}\times x=\dfrac{43}{10}\)
\(\Leftrightarrow x=\dfrac{43}{10}\div\dfrac{1}{2}\)
\(\Leftrightarrow x=\dfrac{43}{5}\)
(-75)+(-7)^2+|-75|+49-(-4)^3
Giải nhanh giúp mình mình cảm ơn trước ạ 🙂
(-75)+(-7)^2+|-75|+49-(-4)^3
= (-75)+49+75+49+64
=2.49+64
=98+64
=162
(-75)+(-7)^2+|-75|+49-(-4)^3
=(-75)+49+75+49+4^3
= -75+49+75+49+64
= (-75+75)+49+49+64
= 0+49+49+64
= 49+49+64
= 2x49+64
= 98+64
= 162
b, 25/x+1 - 1 1/6 = -1/3 - 0,5
c, (2x + 25 3/5 ) mũ 2 - 9/25 = 0
có ai trả lời nhanh nhanh giúp mình với ạ , mình cảm ơn mọi người nhiều lắm ạ .
`a)25/(x+1)-1 1/6=-1/3-0,5`
`=>25/(x+1)=-1/3-1/2+1+1/6`
`=>25/(x+1)=1/3`
`=>75=x+1`
`=>x=74`
Vậy `x=74`
`b)(2x+25 3/5)^2-9/25=0`
`=>(2x+128/5)=9/25`
`**2x+128/5=3/5`
`=>2x=-125/5=-25`
`=>x=-25/2`
`**2x+128/5=-3/5`
`=>2x=-131/5`
`=>x=-131/10`
Giải:
a) \(\dfrac{25}{x+1}-1\dfrac{1}{6}=\dfrac{-1}{3}-0,5\)
\(\dfrac{25}{x+1}=\dfrac{-5}{6}+\dfrac{7}{6}\)
\(\dfrac{25}{x+1}=\dfrac{1}{3}\)
\(\Rightarrow1.\left(x+1\right)=25.3\)
\(\Rightarrow x+1=75\)
\(\Rightarrow x=75-1\)
\(\Rightarrow x=74\)
b) \(\left(2x+25\dfrac{3}{5}\right)^2-\dfrac{9}{25}=0\)
\(\left(2x+\dfrac{128}{5}\right)^2=0+\dfrac{9}{25}\)
\(\left(2x+\dfrac{128}{5}\right)^2=\dfrac{9}{25}\)
\(\Rightarrow\left[{}\begin{matrix}\left(2x+\dfrac{128}{5}\right)^2=\left(\dfrac{3}{5}\right)^2\\\left(2x+\dfrac{128}{5}\right)^2=\left(\dfrac{-3}{5}\right)^2\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}2x+\dfrac{128}{5}=\dfrac{3}{5}\\2x+\dfrac{128}{5}=\dfrac{-3}{5}\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x=\dfrac{-25}{2}\\x=\dfrac{-131}{10}\end{matrix}\right.\)
Chúc bạn học tốt!
Câu 1.Tính
a) 3/4 + 4/5 x 10/6 =
b) 3/8 - 2/3 : 3/8 =
Giúp mình 2 câu này với mình cảm ơn ạ
a) = 3/4 + 4/3 = 25/12
b) = 3/8 - 16/9 = -101/72 * hình như hơi sai sai:"> *
so sánh nhịp 2/4, 3/4, 4/4 với nhịp 3/8. Huhu giúp mình với mai kiểm trai rồi, mình cảm ơn nhiều ạ.
Tính nhanh:
(7/111 - 4/33 + 9/37) . ( 1/2 - 1/3 - 1/6 )
giúp mình v ạ mình đag cần gấp cảm ơn
(7/111 - 4/33 + 9/37).(1/2 - 1/3 -1/6)
= (7/111 - 4/33 + 9/37).0
= 0
Tính nhanh:
(7/111 - 4/33 + 9/37) . ( 1/2 - 1/3 - 1/6 )
giúp mình v ạ mình đag cần gấp cảm ơn
(7/111 - 4/33 + 9/37).(1/2 - 1/3 - 1/6)
= (7/111 - 4/33 + 9/37).0
= 0