When is the graph of f (x) = 2x2 – 5x – 3 negative?
1 answer:
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Answer:
-1/2 < x < 3
Step-by-step explanation:
First you need to find the x-intercepts. Since the leading coefficient is positive, you know the graph is decreasing through the left x-intercept, so will be negative between the x-intercept values.
f(x) = 2x^2 -5x -3
f(x) = 2x^2 -6x +x -3
f(x) = 2x(x -3) +1(x -3)
f(x) = (2x +1)(x -3)
The x-intercepts are the values of x that make these factors zero:
2x +1 = 0 ⇒ x = -1/2
x -3 = 0 ⇒ x = 3
The graph of f(x) is negative on the interval ...
-1/2 < x < 3
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You can solve this analytically to get
.. 55000*(1 +x/100)^10 = 108193
.. (1 +x/100)^10 = 108193/55000
.. 1 +x/100 = (108193/55000)^(1/10)
.. x = 100*((108193/55000)^(1/10) -1) ≈ 7.00
but I find it just as fast to have a graphing calculator do it.
The city's population is increasing 7% per year.
.. 55000*(1 +x/100)^10 = 108193
.. (1 +x/100)^10 = 108193/55000
.. 1 +x/100 = (108193/55000)^(1/10)
.. x = 100*((108193/55000)^(1/10) -1) ≈ 7.00
but I find it just as fast to have a graphing calculator do it.
The city's population is increasing 7% per year.