precalculus
posted by Jayson on .
Help appreciated~
1.Use the quadratic formula to determine when f(x)= x^2 +7x + 7 is greater than 0. Round your answer to two decimal places.
a) x<5.79, x>1.21
b) x<7, x>1
c) 1<x<7
d) 5.79<x<1.21

2. On what interval will the function f(x) = x^2  5x 6 have a positive rate of change?
a) 1<x<6
b) x>2.5
c) x<1, x>6
d) x is less than or equal to 2.5

1.
find the roots of the function: (7 +/ sqrt(21))/2 = 5.79 and 1.21
Since the graph is a parabola which opens up, it will lie below the xaxis between the roots, and above the axis elsewhere.
A is the answer
2.
Again, you have a parabola which opens up. If you can find the vertex, f(x) will be decreasing on the left, and increasing on the right of the vertex.
The vertex, natch, is at x = b/2a = 5/2.
So, B is the answer