<span>In the function "y=x2-18x" the goal is to find the value of the letter x. We know that y equals x2-18x. First, recognize that x2 is the same thing as 2x. So changing the problem to "y=2x-18x". We can subtract 18x from 2x, which leaves us with -16x. Now the problem looks like this: y=-16x. In order to get x by itself, we will need to do the same thing to both sides of the equation. In this case, we want the answer to be x by itself, or (1x) which is the same thing. We divide both sides of the equation by (-16). We are left with the following: y/-16=x. Basically, in words, x equals y divided by negative 16.</span>
Regroup terms
Add 2x to both sides
Simplify 4 - x + 2x to 4 + x
subtract 4 from both sides
subtract -6 - 4.
Answer: x = -10
I believe the fastest way to solve this problem is to take any two of the given points and to find the slope and y-intercept of the line connecting those two points.
Let's choose the 2 given points (-3,16) and (-1,12).
Going from the first point to the second, the increase in x is 2 and the increase in y is actually a decrease: -4. Thus, the slope of the line connecting these two points is m = -4/2, or m = -2.
Now use the slope-intercept formula to find the y-intercept, b.
One point on the line is (-3,16), and the slope is m = -2.
Thus, the slope-intercept formula y = mx + b becomes 16 = -2(-3) + b.
Here, b comes out to 10.
So now we have the slope and the y-intercept. Write the equation:
y = mx + b becomes y=-2x+10. Which of the four given answer choices is the correct one?
x = -2, x = 5
=> f(x) = a(x+2)(x-5), a ∈ R
