Question

a) tìm a,b,c biết \(\frac{a}{2}=\frac{b}{3}=\frac{c}{4}\) và a + 2b - 3c = -20

b) tìm m,n,p biết \(\frac{m}{2}=\frac{n}{3}=\frac{p}{4}\) và m² - n² +2p² = 108

 

Answer 1

\(a,\frac{a}{2}=\frac{b}{3}=\frac{c}{4}\Rightarrow\frac{a}{2}=\frac{2b}{6}=\frac{3c}{12}\)

\(\Leftrightarrow\frac{a+2b-3c}{2+6-12}=\frac{-20}{-4}=5\)

Vậy: \(a=5.2=10\)

\(b=5.6:2=15\)

\(c=5.12:3=20\)

Answer 2

sao con gai ma de anh con trai vay cau trac nghich lam nhi

Answer 3

b, Ta có :

\(\frac{m}{2}=\frac{n}{3}=\frac{p}{4}=\frac{m^2}{4}=\frac{n^2}{9}=\frac{p^2}{16}\)

\(\Rightarrow\frac{m^2}{4}=\frac{n^2}{9}=\frac{2p^2}{32}=\frac{m^2-n^2+2p^2}{4-9+32}=\frac{108}{27}=4\)

Do đó :

\(\frac{m^2}{4}=4\Leftrightarrow m^2=16\Leftrightarrow m=\pm4\)

\(\frac{n^2}{9}=4\Leftrightarrow n^2=36\Leftrightarrow n=\pm6\)

\(\frac{2p^2}{32}=4\Leftrightarrow2p^2=128\Leftrightarrow p^2=64\Leftrightarrow p=\pm8\)

Vậy : ...