Question : If $4x^{2}=15^{2}–9^{2}$, then the value of $x$ is:
Option 1: 9
Option 2: 6
Option 3: 3
Option 4: 12
Correct Answer: 6
Solution :
Given: $4x^{2}=15^{2}–9^{2}$
According to the formula of $a^{2}–b^{2}=(a–b)(a+b)$,
⇒ $4x^{2}=(15–9)(15+9)$
⇒ $4x^{2}=6×24$
⇒ $x^{2}=6×6$
⇒ $x=\sqrt{36}$
⇒ $x=6$
Hence, the correct answer is 6.
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