Question

[OoO Kún Chảnh OoO]

a)cho biet : a+b/a-b=c+a/c-a

chứng minh rằng : a^2=bc

b) cho 4 so kha c0 : a1;a2;a3;a4 thoa man a2^2= a1.a3

a3^2= a2.a4 

cmr :
\(\frac{a1^3+a2^3+a3^3}{a2^3+a3^3+a4^3}=\frac{a1}{a4}\)

Answer 1

[Minh Triều]

\(a,\frac{a+b}{a-b}=\frac{c+a}{c-a}\Rightarrow\frac{a+b}{c+a}=\frac{a-b}{c-a}=\frac{a+b+a-b}{c+a+c-a}=\frac{2a}{2c}=\frac{a}{c}\)

\(\text{Suy ra: }\frac{a+b}{c+a}=\frac{a}{c}\Rightarrow c.\left(a+b\right)=a.\left(c+a\right)\Rightarrow ac+bc=ac+a^2\)

=>a²=bc

b)Viết đề rõ lại giúp