real solution

no. of real solution of
2x/2+(√2+1)x=(5+2√2)x/2 is

3 Answers

1
ith_power ·

please edit the question

62
Lokesh Verma ·

t=√2
v=√2+1

tx + vx =(t2+v2)x/2

x=2 is one root.. i cant see others but then I may be wrong!

341
Hari Shankar ·

If we write as (t2)x/2+(v2)x/2 = (t2+v2)x/2 and set x/2 = y,

the equation becomes

ay+by=(a+b)y

Dividing by by, we get

1+ky = (1+k)y where 0< k = a/b<1

We will prove that equality occurs only when y = 1

Suppose y<0, then LHS>1 but RHS<1 so equality cannot occur

Consider f(y) = (1+k)y-ky -1

For y>0, (1+k)y increases monotonically.
ky decreases monotonically (k<1), so that -ky increases monotonically

Now we can therefore infer that (1+k)y-ky -1 is a monotnically increasing continuous function

f(0) = -1, f(1) = 0. Thus f(y)<0 for 0≤y<1 and f(y)>0 for y>1

Hence there are no solutions other than y = x/2 = 1. Hence x =2 is the only solution

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