Question

[minh khanh]

C = (a+2xb)+(b+2xc)+(c+2xa)

Với a+b+c=15    

Mình cần gấp .    

Answer 1

[Nguyễn Việt Hoàng]

\(C=\left(a+2\times b\right)+\left(b+2\times c\right)+\left(x+2\times a\right)\)

\(\Leftrightarrow C=a+b+c+2\times b+2\times c+2\times a\)

\(\Leftrightarrow C=\left(a+b+c\right)+2\left(a+b+c\right)\)

\(\Leftrightarrow C=\left(a+b+c\right)\left(2+1\right)=15.3=45\)

Answer 2

[Vũ Cao Minh⁀ᶦᵈᵒᶫ ( ✎﹏IDΣΛ亗 )]

\(C=\left(a+2\times b\right)+\left(b+2\times3\right)+\left(c+2\times a\right)\)

\(C=a+2\times b+b+2\times c+c+2\times a\)

\(C=\left(a+b+c\right)+\left(2a+2b+2c\right)=15+2\left(a+b+c\right)\)

\(=15+2\times15=15+30=45\)