y = x2 + 6x + 7
a = 1, b = 6, c = 7
Since a is positive, the graph opens upward. You can find the vertex coordinates (-b/2a, f(-b/2a)) = (-3, f(-3)) = (-3, -2), so the equation of the axis of symmetry is x = -b/2a = -3, plot the y-intercept point (0, 7), plot the point (-b/a, 7) = (-6, 7), and draw the graph that passes through these points.
Or complete the square.
y = x2 + 6x + 7
y = x2 + 6x + 9 - 9 + 7
y = (x2 + 6x + 9) - 2
y = (x + 3)2 - 2
So start with the graph of y = x2 whose vertex is at the origin. Move it 3 units to the left, and 2 units do
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The quadratic expression x2+6x+8 when factorised equals (x+2)(x+4)
one
(3, -21)
y = x2 - 6x + 2 y = x2 - 6x + 9 - 7 y = (x - 3)2 - 7
the graph is moved down 6 units