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5x/2 -2x =1

6 Answers

62
Lokesh Verma ·

Hint:

\left(1/2+2 \right)^{x/2}=\frac{1}{2^{x/2}}+2^{x/2}

So we have (a+b)x=ax+bx

341
Hari Shankar ·

Else:

let f(y) = yx/2

Then by Lagrange Mean Value Theorem

5^{\frac{x}{2}} - 4^{\frac{x}{2}} = \frac{x}{2} \ t^{\frac{x}{2}-1}, t \in (4,5)

Let g(x) = \frac{x}{2} \ t^{\frac{x}{2}-1}

Then for x>2 g(x)>1 and for x<2, g(x) <1. for x=2 g(x) =1.

Hence x=2 is the unique solution

1
avik ·

i didnt undersatnd #2 sir. help

1
Ricky ·

Well , the graph pretty much sums it up :)

62
Lokesh Verma ·

in #2 i have rewriten the question in the form (x+y)n R (xn+yn)

W0hich is same as proving (x/y+1)n R (x/y)n+1

Which issame as (1+a)n R (1+a)

If a is not equal to zero... then if the two sides are equal, n=1

So in hte above question x/2=1

hence x=2 is the solution...

62
Lokesh Verma ·

@Prophet Sir.. awesome proof [1]

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