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# For all positive integers x, f(x)=f(x+1). If f(3)=15, then what is f(7

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Re: For all positive integers x, f(x)=f(x+1). If f(3)=15, then what is f(7 [#permalink]
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f(x)=f(x+1)
f(3)=15
=>f(3)=f(3+1)=f(4)=f(4+1)=f(5)=f(5+1)=f(6)=f(6+1)=f(7)=15

so Answer is C

Originally posted by sunita123 on 27 Jan 2015, 16:05.
Last edited by sunita123 on 28 Jan 2015, 21:55, edited 1 time in total.
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Re: For all positive integers x, f(x)=f(x+1). If f(3)=15, then what is f(7 [#permalink]
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Here we go---

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

f(3) = 15 ----(2)

Now

f(7) = f(6+1)-----> f(6) = f(5+1)-------> f(5) = f(4+1) ------> f(4) = F(3+1)---> f(3) = 15

Now backtrack
f(4) = 15-----> f(5) = 15 ------> f(6) = 15 ----> f(7) = 15

Though I picked option C

I am still not 100% sure of the answer(don't know why)

My bets on C.
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Re: For all positive integers x, f(x)=f(x+1). If f(3)=15, then what is f(7 [#permalink]
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It is given that: f(x) = f(x+1) implying,
for any value of x, f(x) and f(x +1) has same value => this function is a constant value function.
so for tis function, f(1) = f(2) = f(3) = .... = f(7) = ... f (n-1) = f(n) = 15.
Hence, Ans is (C).
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Re: For all positive integers x, f(x)=f(x+1). If f(3)=15, then what is f(7 [#permalink]
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f(3) = f(4) = f(5) = f(6) = f(7) = 15

Answer = C
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Re: For all positive integers x, f(x)=f(x+1). If f(3)=15, then what is f(7 [#permalink]
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f(x) = f(x+1) means,
for any x, f(x) and f(x +1) has same value
so f(1) = f(2) = f(3) = f(x) = f(x+1)= 15.
Hence, Ans is (C).
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Re: For all positive integers x, f(x)=f(x+1). If f(3)=15, then what is f(7 [#permalink]
F(3)=f(4)= F(5)=f(6)=f(7)=15

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Re: For all positive integers x, f(x)=f(x+1). If f(3)=15, then what is f(7 [#permalink]
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Re: For all positive integers x, f(x)=f(x+1). If f(3)=15, then what is f(7 [#permalink]
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