We have
x² + 24x = 17 (1)
Note that
(x + 12)² = x² + 24x + 144
By adding 144 to the left side of equation (1), it becomes a perfect square.
Therefore
x² + 24x = (x+12)² - 144 (2)
Substitute (2) into (1).
(x + 12)² - 144 = 17
(x + 12)² = 17 +144
(x + 12)² = 161
Answer:
We added 144 to the left side of equation (1) in order to make it a perfect square.
