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Expansions — MATHEMATICS STD 9 — Question

ICSE BoardEnglish MediumSTD 9MATHEMATICSExpansions4 Marks
Question
If $\frac{a}{b}=\frac{b}{c}$, prove that $(a+b+c)(a-b+c)=\left(a^2+b^2+c^2\right)$.
✓

Answer

[Hint. Let $\frac{a}{b}=\frac{b}{c}=k$. Then, $b=c k$ and $a=b k$.$\therefore b=c k$ and $a=c k^2$.
Put these values in required identity and show that L.H.S. $=$ R.H.S.]

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