Question on: JAMB Mathematics - 2023
Find the value of y, if log (y + 8) + log (y - 8) = 2log 3 + 2log 5
y = ±5
y = ±10
y = ±17
y = ±13
Let's solve the given logarithmic equation:
\[ \log(y + 8) + \log(y - 8) = 2\log 3 + 2\log 5 \]
We can use logarithmic properties to simplify the equation. The sum of logarithms is equal to the logarithm of their product:
\[ \log((y + 8)(y - 8)) = \log(3^2 \cdot 5^2) \]
Now, we can set the arguments equal to each other:
\[ (y + 8)(y - 8) = 3^2 \cdot 5^2 \]
Expand and simplify the equation:
\[ y^2 - 64 = 9 \cdot 25 \]
\[ y^2 = 9 \cdot 25 + 64 \]
\[ y^2 = 225 + 64 \]
\[ y^2 = 289 \]
Now, take the square root of both sides:
\[ y = \pm \sqrt{289} \]
So, \( y = \pm 17 \).
Therefore, the correct answer is \( y = \pm 17 \)
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