Question 442586
If you know the factors of 42, you can conclude that x = 3, because 3*(2*3 + 8) = 42. I would only try this if time was a major concern (e.g. during a competition, if it was my last 2 minutes of the SAT, etc.). However it's advised to show your work, as follows:


Given the area, width, and length, we can construct an equality:


*[tex x(2x + 8) = 42]


*[tex 2x^2 + 8x - 42 = 0 \Rightarrow x^2 + 4x - 21 = 0]


This factors to


*[tex (x-3)(x+7) = 0]. The only positive solution is x = 3, so the dimensions are 3 and 14.