[ 2 posts ]

 Print view Previous topic | Next topic

Author Message
 Post subject: Quadratic Equation Help  Posted: Mon Jul 16, 2012 9:44 pm
 Forum Guests

Posts: 1
 I have been going through the flash cards and came across this one for EIVs. Is the statement sufficient?What are the solutions to the equation x^2 + kx - 10 = 0, where k is a constant?(1) One of the solutions is -5.I was able to find the other solution plugging the numbers in.(x+5) (x-2) since the two numbers in the parentheses need to equal -10 when multiplying.But I am scratching my head when plugging them into the equation to solve.

 Post subject: Re: Quadratic Equation Help  Posted: Thu Jul 19, 2012 7:31 am
 ManhattanGMAT Staff

Posts: 8179
 pmvartanian wrote:I have been going through the flash cards and came across this one for EIVs. Is the statement sufficient?What are the solutions to the equation x^2 + kx - 10 = 0, where k is a constant?(1) One of the solutions is -5.I was able to find the other solution plugging the numbers in.(x+5) (x-2) since the two numbers in the parentheses need to equal -10 when multiplying.But I am scratching my head when plugging them into the equation to solve.you've actually got the more sophisticated solution here, so, nice job.you can also solve by just plugging -5 in for x, since it's a solution of the equation (according to what you're told). if you plug that number in, you get 25 - 5k - 10 = 0, or 15 - 5k = 0. therefore, k = 3.this gives you the equation x^2 + 3x - 10 = 0, which can be factored as you've shown above.the best thing, of course, is to get both of these solution methods under your belt. _________________Being well-dressed gives a feeling of inward tranquillity [that] religion is powerless to bestow.C.F. Forbes

Display posts from previous:  Sort by

[ 2 posts ]

#### Who is online

 Users browsing this forum: No registered users and 1 guest

 You cannot post new topics in this forumYou cannot reply to topics in this forumYou cannot edit your posts in this forumYou cannot delete your posts in this forumYou cannot post attachments in this forum

Search for:
 Jump to:  Select a forum ------------------ Ask An Instructor    General GMAT Strategy Questions    GMAT Math       General Math Questions       GMAT Prep Math       Manhattan GMAT CAT Math       Manhattan GMAT Non-CAT Math       Official Guide Math    GMAT Verbal       General Verbal Questions       GMAT Prep Verbal       Manhattan GMAT CAT Verbal       Manhattan GMAT Non-CAT Verbal       Official Guide Verbal    GMAT Integrated Reasoning (IR)       GMAT Prep IR       Manhattan GMAT CAT IR       Manhattan GMAT Non-CAT IR    GMAT AWA Essays Manhattan GMAT    Ask Student Services    Study Groups    GMAT Test Day    Test Centers    Instructor Feedback    Course Feedback B-School    Ask an mbaMission Admissions Consultant    B-School Essays    Business Schools    Professional Networking