tim cac so tu nhien a,b(a khac 0) thoa man:
\(\frac{1}{a}-\frac{b}{6}=\frac{1}{3}\)
AI GIAI DUOC MINH CHO 30 TICK
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tim cac bo 2 so tu nhien a,b khac 0 thoa man: 1/a+1/b=5/6
tim cac so tu nhien a,b thoa man dieu kien \(\frac{11}{17}<\frac{a}{b}<\frac{23}{29}\)va 8b-9a=31
Cho cac so a,b khac nhau va thoa man \(a+\frac{1}{a}=b+\frac{1}{b}\) Chung minh ab=1
tim cac so tu nhien a,b thoa man dieu kien \(\frac{11}{17}\)<\(\frac{A}{B}\)<\(\frac{23}{29}\)
a)Tim cac so tu nhien a,b,c nho nhat khac 0 sao cho :16.a=25.b=30.c
B)tim so tu nhien n<30 de 3n+4 va 5n + 1 co uoc chung khac 1
Giup minh giai cau nay voi: ( Chi nhung ai gioi Toan lop 7 tro len moi giai duoc)Cau 1: Cho frac{1}{c} frac{1}{2} (frac{1}{a}+frac{1}{b} ) ( voi a, b, c khac 0 ; b khac c )C/m rang frac{a}{b}frac{a-c}{c-b} Cau 2: Tim cac gia tri cua x,y thoa man :|2x-27|^{2011}+left(3y+10right)^{2012}0
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Giup minh giai cau nay voi: ( Chi nhung ai gioi Toan lop 7 tro len moi giai duoc)
Cau 1: Cho \(\frac{1}{c}\) = \(\frac{1}{2}\) (\(\frac{1}{a}+\frac{1}{b}\) ) ( voi a, b, c khac 0 ; b khac c )
C/m rang \(\frac{a}{b}=\frac{a-c}{c-b}\)
Cau 2: Tim cac gia tri cua x,y thoa man :
\(|2x-27|^{2011}+\left(3y+10\right)^{2012}=0\)
\(\frac{1}{c}=\frac{1}{2}.\left(\frac{1}{a}+\frac{1}{b}\right)\Rightarrow\frac{1}{c}=\frac{a+b}{2ab}\Rightarrow c=\frac{2ab}{a+b}\)
\(\frac{a-c}{c-b}=\frac{a-\frac{2ab}{a+b}}{\frac{2ab}{a+b}-b}=\frac{\frac{a^2+ab-2ab}{a+b}}{\frac{2ab-ab-b^2}{a+b}}=\frac{a^2+ab-2ab}{2ab-ab-b^2}=\frac{a.\left(a-b\right)}{b.\left(a-b\right)}=\frac{a}{b}\)(ĐPCM)
\(\left|2x-27\right|^{2017}+\left(3y+10\right)^{2012}\Rightarrow\hept{\begin{cases}2x-27=0\\3y+10=0\end{cases}}\Rightarrow\hept{\begin{cases}x=\frac{27}{2}\\y=-\frac{10}{3}\end{cases}}\)(làm tắt nha, có gì bn thêm vào)
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câu 2 : | 2x - 27 |\(^{2011}\)+ ( 3y + 10 ) \(^{2012}\)=0
=> \(\left|2x-27\right|^{2011}\)lớn hơn hoặc = 0 (1)
=> \(\left(3y+10\right)^{2012}\)>hoặc = 0(2)
mà (1) + (2) =0
nên => \(\left|2x-27\right|^{2011}=0\)và \(\left(3y+10\right)^{2012}=0\)
\(\left|2x-27\right|^{2011}=0^{2011}\) \(\left(3y+10\right)^{2012}=0^{2012}\)
\(\left|2x-27\right|=0\) 3y + 10 = 0
2x = 27 3y = -10
x = 27 : 2 y = -10 : 3
x = 13,5 y = \(\frac{-10}{3}\)
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1, Ta có : \(\frac{1}{c}=\frac{1}{2}\left(\frac{1}{a}+\frac{1}{b}\right)\)
\(\Rightarrow\frac{1}{c}.2=\frac{1}{a}+\frac{1}{b}\)
\(\Rightarrow\frac{2}{c}=\frac{a+b}{ab}\)
\(\Rightarrow2ab=c\left(a+b\right)\)
\(\Rightarrow2ab=ac+bc\)
\(\Rightarrow2ab-ab-bc=ac+bc-ab-bc\)
\(\Rightarrow ab-bc=ac-ab\)
\(\Rightarrow b\left(a-c\right)=a\left(c-b\right)\)
\(\Rightarrow\frac{a}{b}=\frac{a-c}{c-b}\)
2, Ta có: \(|2x-27|^{2017}+\left(3y+10\right)^{2012}=0\)
Mà \(|2x-27|^{2017}+\left(3y+10\right)^{2012}\ge0\)
\(\Rightarrow|2x-27|^{2017}=0;\left(3y+10\right)^{2012}=0\)
\(\Rightarrow2x-27=0;3y+10=0\)
\(\Rightarrow2x=27;3y=10\)
\(\Rightarrow x=\frac{27}{2};y=\frac{10}{3}\)
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Xem thêm câu trả lời
cho cac so tu nhien khac 0:a va b thoa man phan so a^2+b^2/ab la so tu nhien. Hay xac dinh quan he giua a va b
tim tat ca cac so tu nhien a, b, c khac 0 va khac nhau sao cho:
\(\frac{1}{a}\) +\(\frac{1}{b}\) +\(\frac{1}{c}\) =1
ta có: a,b,c thuộc n nên;
1:a+1:b+1:c=1
1:(a+b+c)=1
a+b+c=1vìa, b, cthuoocj N, nên a=0 thìb=0vafc=1
hoặc a=1 thì bvafc=0
hoăcj
b=1 thì a,c=0
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tim cac so tu nhien a va b de thoa man (5a+7b)/(6a+5b)=29/28 va (a;b)=1
ai lam duoc em cam on nhieu va hau ta han hoi