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If f(x)=x^2−9 and g(x)=16x−73, for which of the following values does
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21 Jan 2022, 06:58
21 Jan 2022, 06:58
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If f(x)=\(x^2−9\) and g(x)=\(16x−73\), for which of the following values does f(x)=g(x)?
A. -27
B. -8
C. 0
D. 8
E. 27
A. -27
B. -8
C. 0
D. 8
E. 27
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Re: If f(x)=x^2−9 and g(x)=16x−73, for which of the following values does
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21 Jan 2022, 09:59
21 Jan 2022, 09:59
1
Carcass wrote:
If f(x)=\(x^2−9\) and g(x)=\(16x−73\), for which of the following values does f(x)=g(x)?
A. -27
B. -8
C. 0
D. 8
E. 27
A. -27
B. -8
C. 0
D. 8
E. 27
STRATEGY: As with all GRE Multiple Choice questions, we should immediately ask ourselves, Can I use the answer choices to my advantage?
In this case, we can definitely test the answer choices.
Now we should give ourselves about 20 seconds to identify a faster approach.
We can also solve the question algebraically, and this may be faster than testing large x-values (such as x = 27).
So I'm going to solve the question algebraically
We want to find a value of x such that: f(x) = g(x)
Substitute to get: x² - 9 = 16x - 73
Since this is a quadratic equation, we must set it equal to zero.
Add 73 to both sides of the equation to get: x² + 64 = 16x
Subtract 16x from both sides: x² - 16x + 64 = 0
Factor: (x - 8)(x - 8) = 0
So, x = 8
Answer: D
gmatclubot
Re: If f(x)=x^2−9 and g(x)=16x−73, for which of the following values does [#permalink]
21 Jan 2022, 09:59
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