If a and b are constants, what is one solution of the equation (x + a)(x - b) = 0?
(1) a = 4
(2) b = 3
if a & B are consteants MGMAT
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- rommysingh
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IS OA E ?rommysingh wrote:If a and b are constants, what is one solution of the equation (x + a)(x - b) = 0?
(1) a = 4
(2) b = 3
Pls post OA
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Uva
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Target question: What is one solution of the equation (x + a)(x - b) = 0rommysingh wrote:If a and b are constants, what is one solution of the equation (x + a)(x - b) = 0?
(1) a = 4
(2) b = 3
Statement 1: a = 4
This means the equation is (x + 4)(x - b) = 0
So, x = -4, is one possible solution to the equation.
Since we can answer the target question with certainty, statement 1 is SUFFICIENT
Statement 2: The b = 3
This means the equation is (x + a)(x - 3) = 0
So, x = 3, is one possible solution to the equation.
Since we can answer the target question with certainty, statement 2 is SUFFICIENT
Answer = D
Aside: I don't think I've seen an official GMAT question ask for ONE solution to a quadratic equation. Typically, we're either asked for the value of a variable or asked some yes/no question about the value of the variable (e.g., "Is x > 3?). What's the source?
Cheers,
Brent
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Forget conventional ways of solving math questions. In DS, Variable approach is the easiest and quickest way to find the answer without actually solving the problem. Remember equal number of variables and equations ensures a solution.
If a and b are constants, what is one solution of the equation (x + a)(x - b) = 0?
(1) a = 4
(2) b = 3
==> In the original condition, x=-a, and thus we have 2 variables -a,b, meaning we need 2 equations to match the number of variables. Since we have 1 each for both (1), (2) the answer is likely C. Using both (1) & (2) together, x=-4,3 is our solution yet it is not unique, and thus NOT sufficient. Therefore the best answer is E
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If a and b are constants, what is one solution of the equation (x + a)(x - b) = 0?
(1) a = 4
(2) b = 3
==> In the original condition, x=-a, and thus we have 2 variables -a,b, meaning we need 2 equations to match the number of variables. Since we have 1 each for both (1), (2) the answer is likely C. Using both (1) & (2) together, x=-4,3 is our solution yet it is not unique, and thus NOT sufficient. Therefore the best answer is E
If you know our own innovative logics to find the answer, you don't need to actually solve the problem.
www.mathrevolution.com
l The one-and-only World's First Variable Approach for DS and IVY Approach for PS that allow anyone to easily solve GMAT math questions.
l The easy-to-use solutions. Math skills are totally irrelevant. Forget conventional ways of solving math questions.
l The most effective time management for GMAT math to date allowing you to solve 37 questions with 10 minutes to spare
l Hitting a score of 45 is very easy and points and 49-51 is also doable.
l Unlimited Access to over 120 free video lessons at https://www.mathrevolution.com/gmat/lesson
l Our advertising video at https://www.youtube.com/watch?v=R_Fki3_2vO8