SOLUTION: I need to expand this quadratic equation: (3r+8)^2 I answered 3r^2-+2(8*3)+64 ,but it was counted wrong. Could anyone help me?

Algebra ->  Equations -> SOLUTION: I need to expand this quadratic equation: (3r+8)^2 I answered 3r^2-+2(8*3)+64 ,but it was counted wrong. Could anyone help me?      Log On


   

Question 550665: I need to expand this quadratic equation:
(3r+8)^2
I answered 3r^2-+2(8*3)+64 ,but it was counted wrong.
Could anyone help me?
Found 2 solutions by jim_thompson5910, josmiceli:
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!

%283r%2B8%29%5E2 Start with the given expression.


%283r%2B8%29%283r%2B8%29 Expand. Remember something like x%5E2=x%2Ax.


Now let's FOIL the expression.


Remember, when you FOIL an expression, you follow this procedure:


%28highlight%283r%29%2B8%29%28highlight%283r%29%2B8%29 Multiply the First terms:%283%2Ar%29%2A%283%2Ar%29=9%2Ar%5E2.


%28highlight%283r%29%2B8%29%283r%2Bhighlight%288%29%29 Multiply the Outer terms:%283%2Ar%29%2A%288%29=24%2Ar.


%283r%2Bhighlight%288%29%29%28highlight%283r%29%2B8%29 Multiply the Inner terms:%288%29%2A%283%2Ar%29=24%2Ar.


%283r%2Bhighlight%288%29%29%283r%2Bhighlight%288%29%29 Multiply the Last terms:%288%29%2A%288%29=64.


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So we have the terms: 9%2Ar%5E2, 24%2Ar, 24%2Ar, 64


9%2Ar%5E2%2B24%2Ar%2B24%2Ar%2B64 Now add every term listed above to make a single expression.


9r%5E2%2B48r%2B64 Now combine like terms.


So %283r%2B8%29%5E2 FOILs to 9r%5E2%2B48r%2B64.


In other words, %283r%2B8%29%5E2=9r%5E2%2B48r%2B64.

Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
+%283r%2B8%29%5E2+
+9r%5E2+%2B+24r+%2B+24r+%2B+64+
+9r%5E2+%2B+48r+%2B+64+ answer
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There's a very simple way to check this
Pick a small prime number like 13
and say +r+=+13+
+%28+3r+%2B+8+%29%5E2+=+%28+39+%2B+8+%29%5E2+
+47%5E2+=+2209+
and
+9r%5E2+%2B+48r+%2B+64+=+9%2A13%5E2+%2B+48%2A13+%2B+64+
+1521+%2B+624+%2B+64+=+2209+
OK