For what positive value of m will the following equation be true if n = 5?
\((m + n)^2 + (m - n)^2 + m^2 + n^2 = 318\)
The answer is m = 18.
Solve for m: 25 + (m - 5)^2 + m^2 + (m + 5)^2 = 318
Expand out terms of the left hand side: 3 m^2 + 75 = 318
Subtract 75 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[discard]
+223 
