Sat math problem

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1

<p>Hi guys I have problem with this question I solved it,but I did something wrong in my equation this is the only question I got wrong math in test 9 from blue book.</p>

<p>xy = 7 and x - y = 5,then x^2 y - xy^2 = ?</p>

<p>1)2
2)12
3)24
4)35
5)70</p>

<p>I solved it like this but I don't there must be something I got wrong.</p>

<p>x(xy) - y(xy);</p>

<p>since we know xy = 49;</p>

<p>x(49) - y(49)</p>

<p>49x - 49y;</p>

<p>49(x - y) since we know x - y = 5</p>

<p>49(5) = 245.</p>

<p>There something I must have done wrong!!!</p>

2

<p>xy(x-y)=x^2y-xy^2</p>

<p>which is basically 5*7 = 35</p>

3

<p>Kieren’s solution is correct. I’m just going to clean it up a bit:</p>

<p>x^2 y-xy^2 = xy(x-y) = 7*5 = 35</p>

4

<p>Basically, you inadvertently thought that xy = 49 when it actually equals 7 so xy=7</p>

5

<p>Thanks guys alot for giving me another way to solve this algebraically I don’t know why I even changed 7 to 49 I guess I have been tired and my brain automatically transformed 7 to its square thats too stupid !!! .</p>

<p>@2400man Yeh Thanks I just noticed it its rlly stupid that I did this my even though it said 7 my brain automatically transformed it to its square!!!.</p>