Alternative Solutions to the Official Practice Tests

MITer94
Fri, 11 Mar 2016 01:58:02 +0000

Correction: “Test 3” should be replaced with “Test 2.”

Here’s another one:

Test 4, Sec. 3, #15 You can do it via the quadratic formula and some algebra, or by picking numbers as @pckeller suggested, but a slight variant involves using the sum of the roots equaling -b/a (as above!). The sum of the roots is k/2, so only (A) or (B) could possibly be correct. Then here I might try picking numbers, e.g. k = 0 and p = 2. Here x = ± 2 is the desired solution, and only (B) works. Alternatively, determine which choice is equivalent to x = sqrt(2p). Tbh, I likely would’ve done it this way if I was very low on time.

The reason why I brought that up was because picking numbers immediately might lead to picking k = 0, but k = 0 and any choice for p wouldn’t work since (B) and (D) would be indistinguishable. Picking a nonzero k works but is probably slower.