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by kvcpk » Fri Oct 01, 2010 1:20 am
pzazz12 wrote:If f(x)=(x-1)/(x+1), then f(2x) is equal to

A. (3f(x)+1)/(f(x)+3)
B. (f(x)+1)/(f(x)+3)
C. (f(x)+3)/(f(x)+1)
D. (f(x)+3)/(f(x)+2)
E. None of these.
f(x)=(x-1)/(x+1)
put x=1
f(1) = 0
put x=2
f(2) = 1/3

so, we should get 1/3 when we put x=1 in the options.
only A and B are left

put x=0, this should be same for f(x) and f(2x)

f(0) = -1

A gives -3+1 / -1+3 = -1 = f(x) = f(2x)

B gives 0

Hence pick A

Hope this helps!!
"Once you start working on something,
don't be afraid of failure and don't abandon it.
People who work sincerely are the happiest."
Chanakya quotes (Indian politician, strategist and writer, 350 BC-275BC)
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by pzazz12 » Fri Oct 01, 2010 4:31 am
kvcpk wrote:
pzazz12 wrote:If f(x)=(x-1)/(x+1), then f(2x) is equal to

A. (3f(x)+1)/(f(x)+3)
B. (f(x)+1)/(f(x)+3)
C. (f(x)+3)/(f(x)+1)
D. (f(x)+3)/(f(x)+2)
E. None of these.
f(x)=(x-1)/(x+1)
put x=1
f(1) = 0
put x=2
f(2) = 1/3

so, we should get 1/3 when we put x=1 in the options.
only A and B are left

put x=0, this should be same for f(x) and f(2x)

f(0) = -1

A gives -3+1 / -1+3 = -1 = f(x) = f(2x)

B gives 0

Hence pick A

Hope this helps!!
thank you,but is there any way to solve this type of problems..............
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by sanabk » Fri Oct 01, 2010 4:15 pm
If f(x)=(x-1)/(x+1), then f(2x) is equal to

f(2x)=(2x-1)/(2x+1)

(3f(x)+1)/(f(x)+3) substitute f(x) and solve
=[3{(x-1)/(x+1)}+1]/[(x-1)/(x+1)+3]
=[3x-3+x+1]/[x-1+3x+3]
=4x-2/4x+2
=(2x-1)/(2x+1)=f(2x)

Here the answer choice is A (luckily), but need to solve each and every choice until the answer choice is equivalent to f(2x).

A
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by pradeepkaushal9518 » Fri Oct 01, 2010 8:09 pm
great praveen
A SMALL TOWN GUY
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by kvcpk » Sun Oct 03, 2010 1:28 pm
pradeepkaushal9518 wrote:great praveen
Thanks Pradeeep :)
"Once you start working on something,
don't be afraid of failure and don't abandon it.
People who work sincerely are the happiest."
Chanakya quotes (Indian politician, strategist and writer, 350 BC-275BC)
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