GRE9367#27and 37

Forum for the GRE subject test in mathematics.
shalale
Posts: 2
Joined: Mon Sep 29, 2014 2:45 am

GRE9367#27and 37

Postby shalale » Mon Sep 29, 2014 2:49 am

Can some explaine the Q27 from GRE9367?
I select B, but the correct answer is A.
I do not know why f(y) should be f(y)^2.
sorry, I can not write the Q here, because I do not have Latex:(
Thanks

.............................................................................................................
about Q 37 also I have problem,
I chose A as answer, because the first row product in 3 , then det =9*3=27 and after that the third row product in -4, then det=27*(-4)=-108,
but answer is -27. I do not know why:( can someone explain that?
Thanks

DDswife
Posts: 58
Joined: Thu Aug 14, 2014 5:29 pm

Re: GRE9367#27and 37

Postby DDswife » Tue Sep 30, 2014 1:17 am

#27

x^2 + z^2 = r^2 in the plane y = y_0, and f(y_0) is the radius.

#37

You are exchanging rows 2 and 3, which gives you a negative 27

Now, to the new row 2 you are adding the new row 3 times a constant. This doesn't change the determinant. If you dont see why, calculate this

|a b|
|c d|

And the same while adding to any line the other one times any number you choose




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