Y = x2 + 8x + 3
y = (x2 + 8x + 16) + (3 - 16) (complete the square)
y + 13 = (x + 4)2 (add 13 to both sides, show the square we completed)
This is "vertex form" where the vertex is (-4, -13)
The roots are the values of x that make y=0,
(0) + 13 = (x + 4)2 (substitute y=0, so we can solve for x)
±√13 = x+4 (take the square root of both sides)
-4±√13 = x (subtract 4 from both sides)
The roots are -4-√13, -4+√13
y = (x2 + 8x + 16) + (3 - 16) (complete the square)
y + 13 = (x + 4)2 (add 13 to both sides, show the square we completed)
This is "vertex form" where the vertex is (-4, -13)
The roots are the values of x that make y=0,
(0) + 13 = (x + 4)2 (substitute y=0, so we can solve for x)
±√13 = x+4 (take the square root of both sides)
-4±√13 = x (subtract 4 from both sides)
The roots are -4-√13, -4+√13