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CEO
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If f(2x  1) = 4x²  4x  8, then f(5) =
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12 Aug 2018, 06:52
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73% (01:17) correct 27% (01:37) wrong based on 125 sessions
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If f(2x  1) = 4x²  4x  8, then f(5) = A) 16 B) 18 C) 36 D) 48 E) 72
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Re: If f(2x  1) = 4x²  4x  8, then f(5) =
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12 Aug 2018, 06:57
GMATPrepNow wrote: If f(2x  1) = 4x²  4x  8, then f(5) =
A) 16 B) 18 C) 36 D) 48 E) 72 \(f(2x1) = 4(x+1)(x2)\)...... When \(x = 3, f(5) = 16.\)
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Re: If f(2x  1) = 4x²  4x  8, then f(5) =
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12 Aug 2018, 07:42
GMATPrepNow wrote: If f(2x  1) = 4x²  4x  8, then f(5) =
A) 16 B) 18 C) 36 D) 48 E) 72 When x=3, 2x1=5 So,\(f(2x1)=f(5)=4*3^2  4*3  8=36128=16\). Ans. (A)
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Re: If f(2x  1) = 4x²  4x  8, then f(5) =
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12 Aug 2018, 08:00
f(2x1)= f(5); when x=3 Put x=3 in the equation 4\(x^2\) 4x  8. The answer is 16. Answer: A.
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Re: If f(2x  1) = 4x²  4x  8, then f(5) =
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12 Aug 2018, 08:24
GMATPrepNow wrote: If f(2x  1) = 4x²  4x  8, then f(5) =
A) 16 B) 18 C) 36 D) 48 E) 72 Another way.. May help in such questions somewhere else..If you look at the equation, you can easily convert the equation ... \(f(2x1)=4x^24x8=4x^24x+19=(2x1)^29\) So it can be literally written as \(f(x)=x^29\), So f (5)=5^29=259=16
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Re: If f(2x  1) = 4x²  4x  8, then f(5) =
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12 Aug 2018, 08:31
Equate 2x1 = 5 you get x=3 Put x=3 36812 16
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Re: If f(2x  1) = 4x²  4x  8, then f(5) =
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12 Aug 2018, 08:54
OA: A f(2x  1) = 4x²  4x  8, then f(5) = ? Trying lengthier method as other methods have been already discussed above Let \(2x1 =y ; x =\frac{y+1}{2}\) \(f(y) = 4(\frac{y+1}{2})^2 4 (\frac{y+1}{2}) 8 =(y+1)^22(y+1)8 =y^2+1+2y2y28=y^29\) \(f(y)=y^29\) \(f(5) =5^29=259=16\)
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Re: If f(2x  1) = 4x²  4x  8, then f(5) =
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04 Feb 2019, 22:30
GMATPrepNow wrote: If f(2x  1) = 4x²  4x  8, then f(5) =
A) 16 B) 18 C) 36 D) 48 E) 72 to find f(5), never go ahead and put the value as 5 in f(2x1) Think how can i get a f(5), when i substitute x = 3 f(5) =36  20 = 16 A
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If f(2x  1) = 4x²  4x  8, then f(5) =
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18 Apr 2019, 08:35
GMATPrepNow wrote: If f(2x  1) = 4x²  4x  8, then f(5) =
A) 16 B) 18 C) 36 D) 48 E) 72 Great responses above!! Here's one more approach: First notice that 4x²  4x  8 looks a lot like (2x  1)² (2x  1)² = (2x  1)(2x  1) = 4x²  4x + 1Now take: f(2x  1) = 4x²  4x  8 Rewrite as: f( 2x  1) = 4x²  4x + 1  9 = ( 2x  1)²  9 In other words, f( something) = something²  9 In general, we can write f(x) = x²  9We're asked to evaluate f( 5) So f( 5) = 5²  9 = 25  9 = 16 Answer: A Cheers, Brent
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If f(2x  1) = 4x²  4x  8, then f(5) =
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