Silviax wrote:
If x^2 - y^2 = 12 and and x-y = 4 then x =
(a) 1.5
(b) 2.5
(c) 3.5
(d) 4.5
(e) 5.5
I tried to solve this problem in a different way than the video explanation does and unfortunately didn't come up with the same answer. Can you tell me what's wrong with my approach?
Solved 2nd equation for x: x = 4+y
I plugged this into the first equation:
(4+y)^2 -y^2 = 12 and then I solved this equation for y.
16+8y+y^2 - y^2 = 12
16+8y = 12
8 y = -4
y = -0.5 ......
and I just now realized that I made one stupid mistake with a +/- sign and that's why my answer was wrong. Finally solved for x by: x= 4 + (-.5) which equals 3.5!
I guess this approach works too.
Right answer is
C! Dear
Silviax,
Yes, that approach does work. It's a very good thing to appreciate that many many math problems have more than one valid solution. In fact, it's often good practice, after you have solved a problem one way, to see if you can solve it in another way. The more you get comfortable with looking for alternative solutions, the more you will be able to see out-of-the-box solutions to harder problems.
Does all this make sense?
Mike
_________________
Mike McGarry
Magoosh Test PrepEducation is not the filling of a pail, but the lighting of a fire. — William Butler Yeats (1865 – 1939)