Label the vertex and y-intercept (2 questions):
[/i]y= x^2 + 4x + 8 and y= (x+4)^2 - 9[i]
Both equations represent parabolas. Note that the vertex is the point at which the curve meets its axis. So, if you shift the origin to the vertex, the co-ordinates of the vertex become (0,0).
Now, y = x
2+4x+8 needs to be expressed in terms of a general parabolic equation. i.e
x2=(constant)
y=> y = (x
2+4x+4)+4
=> (y-4) = (x+2)
2Now, I'll shift the origin to (-2,4). So that X = 0, Y = 0, represent the vertex, where
X = x+2;
Y= y-4,
X = 0, Y = 0.
=> x+2 =0, y-4 = 0
=> x = -2, y = 4 ....(those are the co-ordinates of the vertex)
The y-intercept is point at which the curve cuts the y-axis, simply put x=0 in the original equation to get the intercept.
Solve (and graph) the inequalities (2 questions)
x^2 - 13x + 30 is < or = 0
and
x^2 + 2x - 35 > 0
=> x
2 - 13x + 30 <=0
You'll need to determine the factors of the equation. In this case,
=> (x-3)(x-10) <=0
Now, plot those numbers along a number line,
<-----(+)------(3)-------(-)--------(10)-----(+)----->
If you plot this quadratic, you'll notice that between the roots i.e. the
interval (3, 10), the quadratic is -ve but for
x = {3, 10}, the quadratic is 0. Also, note that for the
interval x<3 and x>10, the quadratic is +ve (hence the signs on the above number line.)
So, the solution set would be,
=> x = [3, 10]
Edit: Forgot the inequality.