Khan/khan-exercises — Issue #11303: Quadratic equation - Need parentheses when squaring a negative
Author: KhanBugz
Created: 2012-01-15 21:39:26+00:00
State: open
Labels: chrome, win7, wrong-or-unclear

The hint for this question has the discriminant (the part under the square root) as -1^2-4*8*-7, when it should be (-1)^2-4*8*-7. The parentheses make a big difference here--otherwise, you should get the wrong answer (though in this case the hint simply computes as if the parentheses were there).

[quadratic_equation.html?seed=117&problem=0](http://sandcastle.khanacademy.org/media/castles/Khan:master/exercises/quadratic_equation.html?seed=117&problem=0&debug)

[Answer timeline](http://sandcastle.khanacademy.org/media/castles/Khan:master/exercises/quadratic_equation.html?seed=117&problem=0&debug&activity=%5B%5B%22hint-activity%22%2C%220%22%2C12%5D%2C%5B%22hint-activity%22%2C%220%22%2C13%5D%2C%5B%22hint-activity%22%2C%220%22%2C14%5D%2C%5B%22hint-activity%22%2C%220%22%2C16%5D%2C%5B%22hint-activity%22%2C%220%22%2C17%5D%2C%5B%22hint-activity%22%2C%220%22%2C24%5D%2C%5B%22hint-activity%22%2C%220%22%2C24%5D%5D)

[]

Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/535.7 (KHTML, like Gecko) Chrome/16.0.912.75 Safari/535.7

MathJax is loaded, ready, queue length: 0