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24 Jan 2016, 06:03
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D
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
5%
(low)
Question Stats:
85% (01:12) correct
15%
(01:13)
wrong
based on 149
sessions
History
Date
Time
Result
Not Attempted Yet
If one root of the equation x^2 − 5x + m = 0 is 10, what is the value of m + 3?
A. 50
B. 10
C. −5
D. −47
E. −50
A. 50
B. 10
C. −5
D. −47
E. −50
25 Jan 2016, 10:55
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Hi All,
As you perform at higher levels on the GMAT, the test will throw you questions based on subjects that you know, but in ways that you're probably not used to thinking about. This question is based on Quadratics, but you have to organize the information 'backwards', using an end result to reconstruct the original equation.
We're told that one root of the equation X^2 − 5X + m = 0 is 10. We can now start to reverse-FOIL this equation....
X^2 - 5X + M = 0
(X-10)(X + ?) = 0
Since the sum of the "O" and "I" in foil is -5X, we can set up the following equation:
-10X + ?X = -5X
?X = 5X
This proves that the missing 'number' in the above equation is 5...
(X-10)(X+5) = 0
X^2 - 10X + 5X - 50 = 0
X^2 - 5X - 50 = 0
The question asks for the value of M + 3. Since M = -50, (M+3) = -47.
Final Answer:
GMAT assassins aren't born, they're made,
Rich
As you perform at higher levels on the GMAT, the test will throw you questions based on subjects that you know, but in ways that you're probably not used to thinking about. This question is based on Quadratics, but you have to organize the information 'backwards', using an end result to reconstruct the original equation.
We're told that one root of the equation X^2 − 5X + m = 0 is 10. We can now start to reverse-FOIL this equation....
X^2 - 5X + M = 0
(X-10)(X + ?) = 0
Since the sum of the "O" and "I" in foil is -5X, we can set up the following equation:
-10X + ?X = -5X
?X = 5X
This proves that the missing 'number' in the above equation is 5...
(X-10)(X+5) = 0
X^2 - 10X + 5X - 50 = 0
X^2 - 5X - 50 = 0
The question asks for the value of M + 3. Since M = -50, (M+3) = -47.
Final Answer:
GMAT assassins aren't born, they're made,
Rich
15 Jun 2016, 03:47
Kudos
Bookmarks
For a quadratic equation if one of roots is given then it satisfies the equation
In equation \(x^2\)\(-\)\(5x\)\(+\)\(m\) = \(0\) , one of the root is given as 10
Substitute \(x\) = \(10\) in the above equation we get
\(10^2\)\(-\)\(5*10\)\(+\)\(m\) = 0
\(m\) =\(-50\)
\(m+3\) = \(-50 + 3\) =\(-47\)
Correct Answer - D
In equation \(x^2\)\(-\)\(5x\)\(+\)\(m\) = \(0\) , one of the root is given as 10
Substitute \(x\) = \(10\) in the above equation we get
\(10^2\)\(-\)\(5*10\)\(+\)\(m\) = 0
\(m\) =\(-50\)
\(m+3\) = \(-50 + 3\) =\(-47\)
Correct Answer - D
