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Which expression is equivalent to (5x − 3y)^2?

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Which expression is equivalent to (5x − 3y)^2?

by AAPL » Tue Oct 31, 2017 9:43 am
Which expression is equivalent to (5x − 3y)^2?

$$A.\ \ 10x−6y$$
$$B.\ \ 25x−9y$$
$$C.\ \ 25x^2−9y^2$$
$$D.\ \ 25x^2−15xy+9y^2$$
$$E.\ \ 25x^2−30xy+9y^2$$

The OA is E.

Can any expert assist me with this PS question please? I need help to solve it. Thanks.
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by [email protected] » Tue Oct 31, 2017 11:26 am
Hi AAPL,

At higher-and-higher score levels, the GMAT will test you on concepts that you know, but in ways that you're probably not used to thinking about.

With this question, the main concept is FOIL-ing (but you're probably not used to doing that math that anything other than individual variables; here, you're doing it with 5X and 3Y).

(5X - 3Y)^2 =
(5X - 3Y)(5X - 3Y) =
25X^2 - 15XY - 15XY + 9Y^2
25X^2 - 30XY + 9Y^2

Final Answer: E

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hi

by Scott@TargetTestPrep » Thu Nov 02, 2017 4:09 pm
AAPL wrote:Which expression is equivalent to (5x − 3y)^2?

$$A.\ \ 10x−6y$$
$$B.\ \ 25x−9y$$
$$C.\ \ 25x^2−9y^2$$
$$D.\ \ 25x^2−15xy+9y^2$$
$$E.\ \ 25x^2−30xy+9y^2$$
Let's expand the given expression:

(5x - 3y)^2 = (5x - 3y)(5x - 3y) = 25x^2 - 30xy + 9y^2

Answer: E

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by EconomistGMATTutor » Fri Nov 03, 2017 2:09 pm
Which expression is equivalent to (5x - 3y)^2?

$$A.\ \ 10x-6y$$
$$B.\ \ 25x-9y$$
$$C.\ \ 25x^2-9y^2$$
$$D.\ \ 25x^2-15xy+9y^2$$
$$E.\ \ 25x^2-30xy+9y^2$$
Hi AAPL,
Let's take a look at your question.

$$\left(5x-3y\right)^2$$
$$=\left(5x-3y\right)\left(5x-3y\right)$$
$$=5x\left(5x-3y\right)-3y\left(5x-3y\right)$$
$$=25x^2-15xy-\left(15xy-9y^2\right)$$
$$=25x^2-15xy-15xy+9y^2$$
$$=25x^2-30xy+9y^2$$

Therefore, Option E is correct.

Hope it helps.
I am available if you'd like any follow up.
GMAT Prep From The Economist
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by Scott@TargetTestPrep » Thu Oct 31, 2019 5:16 pm
AAPL wrote:Which expression is equivalent to (5x − 3y)^2?

$$A.\ \ 10x−6y$$
$$B.\ \ 25x−9y$$
$$C.\ \ 25x^2−9y^2$$
$$D.\ \ 25x^2−15xy+9y^2$$
$$E.\ \ 25x^2−30xy+9y^2$$

The OA is E.

Can any expert assist me with this PS question please? I need help to solve it. Thanks.
Let's expand the given expression:

(5x - 3y)^2 = (5x - 3y)(5x - 3y) = 25x^2 - 30xy + 9y^2

Answer: E

Scott Woodbury-Stewart
Founder and CEO
[email protected]

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See why Target Test Prep is rated 5 out of 5 stars on BEAT the GMAT. Read our reviews

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