[tex] \sqrt{ - x + 72} = x \\ = > {( \sqrt{ - x + 72)} }^{2} = {x}^{2} \\ = > - x + 72 = {x}^{2} \\ = > {x}^{2} + x - 72 = 0 \\ = > {x}^{2} + 9x - 8x - 72 = 0 \\ = > x(x + 9) - 8(x + 9) = 0 \\ = > (x - 8)(x + 9) = 0 \\ = > x = 8 \: \: or \: \: - 9[/tex]
Answer:
x = 8 or -9
Hope you could get an idea from here.
Doubt clarification - use comment section.
