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Question: Answered & Verified by Expert
If $3^{(x-1)}+3^{(x+1)}=30$, then what is the value of $3^{(x+2)}+3^{x}$ ?
MathematicsSets and RelationsNDANDA 2007 (Phase 1)
Options:
  • A 30
  • B 60
  • C 81
  • D 90
Solution:
1380 Upvotes Verified Answer
The correct answer is: 90
Given: $3^{(x-1)}+3^{(x+1)}=30$
$\Rightarrow \frac{3^{\mathrm{x}}}{3}+3.3^{\mathrm{x}}=30$
Multiplying both the sides by 3 in equation (i) $3^{x}+3^{2} .3^{x}=90$
$\Rightarrow 3^{\mathrm{x}}+3^{\mathrm{x}+2}=90$

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