tính hợp lý bài
0.25x12
tính hợp lý bài
0.25x12
`0,25xx12`
`=1/4xx12`
`=(1xx12)/4`
`=12/4`
`=3`
5/12 - 3/-16 +3/4
giúp mình với
`5/12-3/(-16)+3/4`
`=5/12-(-3/16)+3/4`
`=5/12+3/16+3/4`
`=20/48+9/48+36/48`
`=29/48+36/48`
`=65/48`
\(\dfrac{5}{12}-\dfrac{3}{-16}+\dfrac{3}{4}\)
\(=\dfrac{5}{12}-\dfrac{-3}{16}+\dfrac{3}{4}\)
\(=\dfrac{80}{192}-\dfrac{-36}{192}+\dfrac{3}{4}\)
\(=\dfrac{29}{48}+\dfrac{3}{4}\)
\(=\dfrac{29}{48}+\dfrac{36}{48}\)
\(=\dfrac{65}{48}\)
\(\dfrac{5}{12}-\dfrac{3}{-16}+\dfrac{3}{4}\)
\(=\dfrac{5}{12}+\dfrac{3}{16}+\dfrac{3}{4}\)
\(=\dfrac{20}{48}+\dfrac{9}{48}+\dfrac{36}{48}\)
\(=\dfrac{65}{48}\)
\(đk:m^2+5\ne0\left(lđ\right)\)
\(\Rightarrow\dfrac{m+2}{m^2+5}\ne0\left(lđ\right)\)
\(\Rightarrow\) Với mọi \(m\in Z\) thì phân số luôn tồn tại
\(\RightarrowĐ\)
Để \(C\) nguyên
\(\Leftrightarrow2n+1\inƯ\left(13\right)\\ Ư\left(13\right)=\left\{1;-1;13;-13\right\}\\ \Leftrightarrow\left\{{}\begin{matrix}2n+1=1\\2n+1=-1\\2n+1=13\\2n+1=-13\end{matrix}\right.\\ \Rightarrow\left\{{}\begin{matrix}n=0\\n=-1\\n=6\\n=-7\end{matrix}\right.\)
Vậy có 4 giá trị n nguyên để giá trị C là một số nguyên
\(đk:6-5x\ne0\\ =>x\ne\dfrac{6}{5}\\ \dfrac{-5}{-14}=\dfrac{20}{6-5x}\\ =>\dfrac{5}{14}=\dfrac{20}{6-5x}\\ =>5\times\left(6-5x\right)=20\times14\\ =>5\times\left(6-5x\right)=280\\ =>6-5x=280:5\\ =>6-5x=56\\ =>5x=6-56\\ =>5x=-50\\ =>x=-10\left(t/mđk\right)\)
\(\dfrac{-5}{-14}=\dfrac{20}{6-5x}\\ \dfrac{5}{14}=\dfrac{20}{6-5x}\\ \dfrac{20}{56}=\dfrac{20}{6-5x}\\ 6-5x=56\\ 5x=6-56\\ 5x=-50\\ x=-50:5\\ x=-10\)
-7/21+(1+1/3) help:<
` -7/21+(1+1/3) =-7/21 + ( 3/3 + 1/3)=-7/21 +4/3= -7/21 + 28/21= 21/21=1`
\(-\dfrac{7}{21}+\left(1+\dfrac{1}{3}\right)\)
\(=-\dfrac{1}{3}+1+\dfrac{1}{3}\)
\(=\left(-\dfrac{1}{3}+\dfrac{1}{3}\right)+1\)
\(=1\)
\(\dfrac{-7}{21}+\left(1+\dfrac{1}{3}\right)=\dfrac{-7}{21}+\dfrac{4}{3}=\dfrac{-7+28}{21}=\dfrac{21}{21}=1\)
bạn tham khảo ở đây: https://lazi.vn/edu/exercise/1218721/mot-lop-hoc-co-48-hoc-sinh-xep-loai-gioi-kha-trung-binh-va-khong-co-hoc-sinh-yeu-kem-so-hoc-sinh-trung-binh-chiem-5-12-so-hoc-sinh
3/17.13/15+3/17.2/15
\(\dfrac{3}{17}\left(\dfrac{13}{15}+\dfrac{2}{15}\right)=\dfrac{3}{17}\times\dfrac{15}{15}=\dfrac{3}{17}\times1=\dfrac{3}{17}\)
`3/17 xx 13/15 + 3/17 xx 2/15 = =3/17xx(13/15 + 2/15)=3/17 xx 1 = 3/17`