find value of x if log2^x+log3^27=0
Answers
Answer:
We know
log(x) ^n = n logx
log2^x + log 3^27 = x log2 + 27 log 3 = 0
x = - 27 log3 / log2
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Before solving the problem, let us know some logarithmic formulae :
• log (a × b) = log (a) + log (b) ..... (i)
• log (aᵇ) = b log (a) ..... (ii)
• log (a) = log (b) gives a = b ..... (iii)
• log (1) = 0 ..... (iv)
Easier way to solve for x :
Here, log (2ˣ) + log (3²⁷) = 0
or, x log (2) + 27 log (3) = 0, using (ii)
or, x log (2) = - 27 log (3)
or, x = - 27 log (3) / log (2)
∴ the required solution is
x = - 27 log (3) / log (2).
Another approach :
Now, log (2ˣ) + log (3²⁷) = 0
or, log (2ˣ * 3²⁷) = log (1) using (i) and (iv)
or, 2ˣ * 3²⁷ = 1 using (iii)
or, 2ˣ = 1/(3²⁷)
or, 2ˣ = 3⁻²⁷
Taking log to both sides, we get
log (2ˣ) = log (3⁻²⁷)
x log (2) = - 27 log (3) using (ii)
or, x = - 27 log (3) / log (2) = - 42.8 (approx.)