tim a b \(\in Q\)
a, a - b = 2 \(\left(a+b\right)=a\div b\)
b, a + b = a . b = a \(\div\) b
giup minh nhe minh dang can gap
tim x
a, \(2,75\div x=0,4\div1,5\)
b, \(3\dfrac{1}{2}\div\left(2x-3\right)=\dfrac{-3}{4}\div0,2\)
c, \(\dfrac{3x+2}{27}=\dfrac{3}{3x+2}\)
d ,\(\dfrac{5-x}{4}=\dfrac{2x+3}{2}\)
giup minh nhe minh dang can gap
a: \(\dfrac{2.75}{x}=\dfrac{0.4}{1.5}=\dfrac{4}{15}\)
\(\Leftrightarrow x=\dfrac{11}{4}\cdot\dfrac{15}{4}=\dfrac{165}{16}\)
b: \(3\dfrac{1}{2}:\left(2x-3\right)=\dfrac{-3}{4}:0.2\)
\(\Leftrightarrow\dfrac{7}{2}:\left(2x-3\right)=\dfrac{-3}{4}:\dfrac{1}{5}=\dfrac{-15}{4}\)
\(\Leftrightarrow2x-3=\dfrac{7}{2}:\dfrac{-15}{4}=\dfrac{-7}{2}\cdot\dfrac{4}{15}=\dfrac{-28}{30}=\dfrac{-14}{15}\)
=>2x=-14/15+3=45/45-14/15=31/45
=>x=31/90
c: \(\dfrac{3x+2}{27}=\dfrac{3}{3x+2}\)
\(\Leftrightarrow\left(3x+2\right)^2=81\)
=>3x+2=9 hoặc 3x+2=-9
=>3x=7 hoặc 3x=-11
=>x=7/3 hoặc x=-11/3
d: \(\dfrac{5-x}{4}=\dfrac{2x+3}{2}\)
=>10-2x=8x+12
=>-10x=2
hay x=-1/5
cho A = 3a - 4ab + 5b . tinh gia tri cua A khi
a, \(\left|a\right|=\dfrac{3}{4},b=\dfrac{-5}{6}\)
b,\(a=\dfrac{-2}{3},b=\dfrac{4}{5}\)
giup minh nhe minh dang can gap
a) Vì |a|=\(\dfrac{3}{4}\)=>a=\(\dfrac{3}{4}\).Thay vào ta sẽ có:
A=3.\(\dfrac{3}{4}\)-4.\(\dfrac{3}{4}\).(\(\dfrac{-5}{6}\))+5.(\(\dfrac{-5}{6}\))
A=\(\dfrac{9}{4}-\left(\dfrac{-5}{2}\right)+\left(\dfrac{-25}{6}\right)\)
A=\(\dfrac{19}{4}\)-\(\dfrac{25}{6}\)
A=\(\dfrac{14}{24}\)=\(\dfrac{7}{12}\)
b, Thay vào, ta sẽ có:
A=3.\(\left(\dfrac{-2}{3}\right)-4.\left(\dfrac{-2}{3}\right).\dfrac{4}{5}+5.\dfrac{4}{5}\)
A=-2-\(\left(\dfrac{-32}{15}\right)\)+4
A=\(\dfrac{2}{15}\)+4
A=\(\dfrac{62}{15}\)
cho \(\dfrac{a}{b}=\dfrac{c}{d}\left(a,b,c,d\ne0\right)\) chung minh rang
a ,\(\dfrac{a+b}{a-b}=\dfrac{c+d}{c-d}\)
b ,\(\dfrac{2a+5b}{3a-4d}=\dfrac{2c+5d}{3c-4d}\)
giup minh nhe minh dang can gap
a. Ta có : ( a + b )( c - d ) = ac-ad+bc-bd (1)
( a - b )( c + d ) = ac+ad-bc+bd (2)
Từ giả thuyết : \(\dfrac{a}{b}=\dfrac{c}{d}\Rightarrow ad=bc\) (3)
Từ (1) , ( 2) và ( 3) \(\Rightarrow\)( a + b )( c - d) = ( a - b)( c + d )
\(\Rightarrow\dfrac{a+b}{a-b}=\dfrac{c+d}{c-d}\left(đpcm\right)\)
chứng minh BĐT:
a,\(\frac{ab}{a+b}+\frac{bc}{b+c}+\frac{ca}{c+a}0\right)\)
cac ban giup minh. minh dang can rat rat gap
bài1 . cho a>=0, b>=0
CMR:\(\frac{a^3+b^3}{2}>=\left(\frac{a+b}{2}\right)^3\)
cac ban oi giup minh nhe. minh can gap. giup minh di. giup minh di chieu minh di hoc roi
Cho a/b =c/d. CMR :
a) a+c/b+d = a-c/b-d.
b) a-b/b = c-d/d.
Ai biet thi chi giup minh voi nhe. Minh dang can gap lam.
Cho bieu thuc A = 3/n-2
a) Tim cac so nguyen n de bieu thuc A la phan so
b) Tim cac so nguyen n de A la mot so nguyen
Cac giup minh nhe minh dang can gap.
tim x
a,\(\left|2x-1,6\right|-2,3=1,4\)
b\(5,4-\left|3x-1,2\right|=5,5\)
c,\(\left|x+1,3\right|+\left|x+2,4\right|=4x\)
d, \(\left|x-1,2\right|+\left|2,5-x\right|=0\)
giup minh nhe minh dang can gap
a/ \(\left|2x-1,6\right|-2,3=1,4\)
\(\Leftrightarrow\left|2x-1,6\right|=3,7\)
\(\Leftrightarrow\left[{}\begin{matrix}2x-1,6=3,7\\2x-1,6=-3,7\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}2x=5,3\\2x=-2,1\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=2,65\\x=-1,05\end{matrix}\right.\)
Vậy ....
b/ \(5,4-\left|3x-1,2\right|=5,5\)
\(\Leftrightarrow\left|3x-1,2\right|=-0,1\)
Mà \(\left|3x-1,2\right|\ge0\)
\(\Leftrightarrow x\in\varnothing\)
c/ \(\left|x+1,3\right|+\left|x+2,4\right|=4x\)
Mà \(\left\{{}\begin{matrix}\left|x+1,3\right|\ge0\\\left|x+2,4\right|\ge0\end{matrix}\right.\) \(\Leftrightarrow4x\ge0\)
\(\Leftrightarrow x+1,3+x+2,4=4x\)
\(\Leftrightarrow2x+3,7=4x\)
\(\Leftrightarrow3,7=4x-2x\)
\(\Leftrightarrow2x=3,7\)
\(\Leftrightarrow x=1,85\)
Vậy ....
d/ \(\left|x-1,2\right|+\left|2,5-x\right|=0\)
Mà \(\left\{{}\begin{matrix}\left|x-1,2\right|\ge0\\\left|2,5-x\right|\ge0\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}\left|x-1,2\right|=0\\\left|2,5-x\right|=0\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x-1,2=0\\2,5-x=0\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=1,2\\x=2,5\end{matrix}\right.\) (loại)
Vậy ..
a, \(\left|2x-1,6\right|-2,3=1,4\)
\(\Rightarrow\left|2x-1,6\right|=3,7\)
\(\Leftrightarrow\left[{}\begin{matrix}2x-1,6=3,7\\2x-1,6=-3,7\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=2,65\\x=-1,05\end{matrix}\right.\)
b,\(5,4-\left|3x-1,2\right|=5,5\)
\(\Rightarrow\left|3x-1,2\right|=-0,1\) (vô lí)
Vì \(\left|x\right|\ge0\) mà \(\left|3x-1,2\right|< 0\)
Vậy, không có giá trị của x thỏa mãn.
c, \(\left|x+1,3\right|+\left|x+2,4\right|=4x\)
\(\Rightarrow\left\{{}\begin{matrix}\left|x+1,3\right|\ge0\\\left|x+2,4\right|\ge0\end{matrix}\right.\Leftrightarrow4x\ge0\)
\(\Leftrightarrow x+1,3+x+2,4=4x\)
\(\Leftrightarrow x+x+1,3+2,4=4x\)
\(\Leftrightarrow2x+3,7=4x\)
\(\Leftrightarrow2x-4x=-3,7\)
\(\Leftrightarrow-2x=-3,7\)
\(\Leftrightarrow x=\dfrac{3,7}{2}\)
d, \(\left|x-1,2\right|+\left|2,5-x\right|=0\)
\(\Rightarrow\left\{{}\begin{matrix}\left|x-1,2\right|\ge0\\\left|2,5-x\right|\ge0\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}\left|x-1,2\right|=0\\\left|2,5-x\right|=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x-1,2=0\\2,5-x=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=1,2\\x=2,5\end{matrix}\right.\)
Tìm a,b,c sao cho
a, \(\frac{1}{x\left(x+1\right).\left(x+2\right)}=\frac{a}{x}+\frac{b}{x+1}+\frac{c}{x+2}\)
cac ban oi giup minh di. minh dang can gap lam. lam on
tick đi giải cho
đáp án là a=4.............