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cowboys93
Jul 8, 2009, 07:34 PM
The question says,Graph the function and determine the intervals for which f(x) is greater than or equal to than 0.

f(x)=4x+2

Help pllleaseee

Perito
Jul 8, 2009, 08:21 PM
You wrote f(x) = 4x +2. What values of this are equal to zero? How about

0 = 4x + 2?

If you solve this for x, you'll see what value of x is zero. You can then figure out what values of x make the function greater than zero.

Let me give you an example. Let's say that you have the equation

f(x) = 17x - 34

We look at the equation

0 = 17x -34
17x = 34
x = 2

So we know that f(x) = 0 for x = 2. What about x > 2? Let's try x=3

f(3) = 17 * 3 - 34 = 17 yup > 0

You can show that for any x > 2, f(x) will be greater than 0.

What about x < 2?

f(1) = 17 * 1 -34 = -17

You can also show that for any x<2, f(x) will be less than zero.

Therefore, for this equation, the intervals for which f(x) >= 0 are x= 2 to x= infinity

You can also solve this equation

17x - 34 >= 0

17x >= 34

x >= 2

We haven't divided by any negative numbers, which would reverse the sign. We've just proven what we saw, above. You do the same thing for your equation:

f(x) = 4x+2 >= 0