Answer:
√(56 - m) = m
Square both sides to clear the radical.
56 - m = m²
Add m to both sides, then subtract 56 from both sides.
m² + m - 56 = 0
Factor this quadratic equation.
(m - 7)(m + 8) = 0
Set each factor equal to zero, and solve for m.
m - 7 = 0 or m + 8 = 0
m = 7 or m = -8
Check each possible solution.
√(56 - 7) = 7--->√49 = 7 (true)
√(56 - (-8)) = -8--->√64 = -8 (false)
-8 is an extraneous solution, so the only solution of the given equation is 7.
m = 7