I´m had been problems to solve by factoring the next equation. (x^2)- 13x-130=0
Is there anyone who can help me to solve it?
Thanks in advance!
First of all, here's a general article on the topic. http://magoosh.com/gmat/2012/algebra-on ... to-factor/
For this question, we need two numbers
(a) whose product is -130, so one is positive and one is negative
(b) whose sum is -13 (so the one with the larger absolute value is negative)
130 = 13*10, but those two numbers are too close
130 = 5*26
130 = 2*65
Those are the only whole number factors that multiply to 130, and none of them work.
The problem is --- this quadratic is 100% unfactorable. The solutions involve expressions with the square-root of 689, which is an unsimplifiable square-root. The GMAT would NEVER ask you to factor such an equation. If this equation appeared in some form on the GMAT, it would have to be a question that could be solved without factoring it. The GMAT would not expect you to find the solutions without a calculator.
Does this make sense?
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