Taking OAR tomorrow!! Need help on one Math Problem!!!

[IT1toOfficer]

Ok folks I need you help. I take the OAR tomorrow and I’m doing my last bit of studying and I came across a problem I’m stuck on. Could someone help me out with this…PLEASE!!!

Ok I can’t write powers on here so I’ll use the following

Sq means “Squared” or to the “second power”

If (X-Y)sq = 40 and Xsq + Ysq = 60, the XY =

Does anyone know how to solve this…Please help.. Maybe I’m an idiot, but I can’t figure it out. I have the answer in the back of the book, but it makes no since.


Thanks.

IT1(SW)

 

[RevnR6]

SQ means neither in that equation. You are looking at it wrong. SQ is simply another variable. If it confuses you write it as SQ=Z

 

[IT1toOfficer]

What do you mean.. do they cross each other out?? How would you solve???

 

[Kathy]

I'm quite a few years out from my math degree, but here goes...

(x-y)sq = 40
(x-y)(x-y) = 40
xsq - xy - xy + ysq = 40
xsq - 2xy + ysq = 40
xsq + ysq - 2xy = 40

Since xsq + ysq = 60...
60 - 2xy = 40
-2xy = -20
xy = 10

 

[Minnie]

The answer

Assuming the squares are in the problem (unlike the last post ):

Multiply out the (x-y)sq to xsq-2xy+ysq = 40

Now solve the other equation for one variable xsq = 60 - ysq

Ok... time to substitute the second equation into the first:

(60-ysq)-2xy+ysq=40

Now solving for xy... (I am keepin the intermediate steps here...)

60-2xy=40
-2xy=-20
xy=10

Hope that helps?

Good luck on your exam!! :icon_smil

Minnie

 

[IT1toOfficer]

I get it now..thank you.. I feel dumb!!!