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For what positive value of m will the following equation be true if n = 5?

(m + n)^2 + (m - n)^2 + m^2 + n^2 = 318.

 Sep 30, 2020
 #1
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(m + n)^2 + (m - n)^2 + m^2 + n^2 = 318.

 

If n = 5, then m = 9

 Sep 30, 2020
 #2
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but how did you do it?

Guest Sep 30, 2020
 #3
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Solve for m:
(m - 5)^2 + m^2 + (m + 5)^2 = 293

Expand out terms of the left hand side:
3 m^2 + 50 = 293

Subtract 50 from both sides:
3 m^2 = 243

Divide both sides by 3:
m^2 = 81

Take the square root of both sides:


m = 9      or        m = -9

Guest Sep 30, 2020

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