To complete the square, in this example, you treat p² - 3p as <em>a² - ab</em> in the equation <em>a² - 2ab + b², or (a - b)²</em>.
So, we say that <em>p² - 3p is p² - 3p + 2.25, or (p - 1.5)²</em>. But his means we have and additional 2.25, so we <em>add that to both sides</em>.
This leaves us <em>(p - 1.5)² = 10.25</em>.
Now, we just take the square root from both sides. <em>p - 1.5 = ±√10.25</em>.
Our solutions are p = 1.5 + √10.25, p = 1.5 - √10.25.