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What if you could take an equation with logarithms scattered on both sides and collapse them all into a single, straightforward quadratic?
In 1614, Scottish mathematician John Napier invented logarithms to turn tedious multiplication into simple addition, and that exact same principle allows us to merge multiple logarithmic terms today.
A logarithm logaβ(y)=x asks the question: "To what power must we raise base a to get y?", which means ax=y with the restriction that base a>0,aξ =1 and the input argument y>0.
Because multiplying powers adds their exponents (auβ
av=au+v), the log of a product splits into the sum of logs: logaβ(M)+logaβ(N)=logaβ(MN).
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How do we use this condensing power to crack an equation with unknown binomials inside the logs?
Condensing and Solving
Let's solve the equation logaβ(x+3)+logaβ(xβ2)=logaβ(6) step by step.
First, we condense the left side into a single logarithm using the product law: logaβ((x+3)(xβ2))=logaβ(6).
By the One-to-One Property (injectivity) of logarithms, if logaβ(A)=logaβ(B) (where a>0,aξ =1), then A=B.
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Expanding and rearranging gives x2+xβ6=6, which simplifies to the standard quadratic equation x2+xβ12=0.
Factoring gives (x+4)(xβ3)=0, yielding two potential algebraic solutions: x=3 and x=β4.