Homework Help: precalculus

Posted by Jayson on Monday, December 19, 2011 at 2:39pm.

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
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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

precalculus - Steve, Monday, December 19, 2011 at 3:11pm
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 x-axis 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

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