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# If A, B, and C Are in Continued Proportion, Prove that (A^2 + Ab + B^2)/(B^2 + Bc + C^2) = A/C - Mathematics

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#### Question

If a, b, and c are in continued proportion, prove that (a^2 + ab + b^2)/(b^2 + bc + c^2) = a/c

#### Solution

Given, a, b and c are in continued proportion.

=> a/b = b/c = k (say)

=> a = bk, b = ck

=> a = (ck)k = ck^2, b = ck

L.H.S  (a^2 + ab + b^2)/(b^2 + bc + c^2)

= ((ck^2)^2 + (ck^2)(ck) + (ck)^2)/((ck)^2 + (ck)c + c^2)

= (c^2k^4 + c^2k^3 + c^2k^2)/(c^2k^2 + c^2k + c^2)

= (c^2k^2(k^2 + k + 1))/(c^2(k^2 + k + 1))

= k^2

RHS = a/c = (ck^2)/c = k^2

∴ LHS = RHS

Is there an error in this question or solution?

#### APPEARS IN

Selina Solution for Concise Mathematics for Class 10 ICSE (2020 (Latest))
Chapter 7: Ratio and Proportion (Including Properties and Uses)
Exercise 7(C) | Q: 10.1 | Page no. 101