cho a/b =b/c CMR a/c =a^2+b^2/b^2 +c^2
giúp mình với nha các bạn cảm ơn
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26 tháng 8 2020
1.It seems that our proposal has been accepted by him
2.It is ly that charges will be press against him
3.It seems that he has forgotten our appointment
4.It seems that your car has been taken by your brother without asking you first
5.Its ly that the school will expel John
6.It seems that she was trying to warn you
7.It seems that Sally lied about it all long
8.My mother will probably be angry when I het home
9.It seems that Mrs.White has got married again
10.My boss will probably resign next year
HK
22
HK
21
AO
4
AO
3
AO
2
26 tháng 8 2020
-> The last time she cook was two day ago
TD
4
Bài làm:
Ta có: \(\frac{a}{b}=\frac{b}{c}\) => \(b^2=ac\)
Thay vào ta được: \(\frac{a^2+b^2}{b^2+c^2}=\frac{a^2+ac}{ac+c^2}=\frac{a\left(a+c\right)}{c\left(a+c\right)}=\frac{a}{c}\)
Vậy \(\frac{a}{c}=\frac{a^2+b^2}{b^2+c^2}\)
Đặt \(\frac{a}{b}=\frac{b}{c}=k\Rightarrow\hept{\begin{cases}a=kb\\b=kc\end{cases}}\Rightarrow a=k^2c\)
\(\frac{a^2+b^2}{b^2+c^2}=\frac{\left(k^2c\right)^2+\left(kc\right)^2}{\left(kb\right)^2+c^2}=\frac{k^4b^c+k^2c^2}{k^2b^2+c^2}=\frac{k^2\left(k^2b^2+c^2\right)}{k^2b^2+c^2}=k^2=\frac{a}{c}\)( đpcm )