Question 879409
<pre>
Remmber the word FOIL.
F = FIRST TERM in each parentheses,
O = OUTER TERMS. (The two terms farthest apart)
I = INNER TERMS. (The two terms in the middle)  
L = LAST TERM in each parentheses

FIRSTS:
(<font color = "red">2r</font>-5)(<font color = "red">2r</font>-5)

2r times 2r gives 4rē

OUTERS
(<font color = "red">2r</font>-5)(2r<font color = "red">-5</font>)

2r times -5 gives -10r

INNERS
(2r<font color = "red">-5</font>)(<font color = "red">2r</font>-5)

-5 times 2r gives -10r

LASTS
(2r<font color = "red">-5</font>)(2r<font color = "red">-5</font>)

-5 times -5 gives +25

Write them all together in a row:

4rē-10r-10r+25

The two middle terms are LIKE TERMS and so they will combine
since -10r plus -10r is -20r.

Answer: 4rē-20r+25

Edwin</pre>