What is the vertex of the parabola y = x² + 8x + 5 ?
y = x² + 8x + 5
a = 1, b = 8, and c = 5 {in standard form}
-b
---- is the x-coordinate of the vertex
2a
-8
------ = x-coordinate of vertex {substituted 1 for a and 8 for b}
2(1)
x-coordinate of vertex is -4 {simplified}
y = x² + 8x + 5 {the equation of the parabola}
y = (-4)² + 8(-4) + 5 {substituted -4 for x into equation to find y-coordinate of vertex}
y = 16 - 32 + 5 {evaluated exponent and multiplied}
y = -11 {added and subtracted}
(-4 , -11) is the vertex of the parabola
- Algebra House
