# Quadratic relationship problems

### Real World Examples of Quadratic Equations

The name Quadratic comes from "quad" meaning square, because the variable gets squared (like x2). It is also called an "Equation of Degree 2" (because of the . Quadratic Equation. Quadratic equations pop up in many real world situations! Here we have collected some examples for you, and solve each using different. Apply quadratic functions to real world situations in order to solve problems. .. The relationship between the cost of an item and the quantity sold is often linear.

See the section on manipulating graphs. Answer Return to Contents Standard Form The functions in parts a and b of Exercise 1 are examples of quadratic functions in standard form.

If a is positive, the graph opens upward, and if a is negative, then it opens downward. Any quadratic function can be rewritten in standard form by completing the square. See the section on solving equations algebraically to review completing the square. The steps that we use in this section for completing the square will look a little different, because our chief goal here is not solving an equation.

Note that when a quadratic function is in standard form it is also easy to find its zeros by the square root principle. Sketch the graph of f and find its zeros and vertex.

### Quadratic Equations

Group the x2 and x terms and then complete the square on these terms. When we were solving an equation we simply added 9 to both sides of the equation. In this setting we add and subtract 9 so that we do not change the function. This is standard form. From this result, one easily finds the vertex of the graph of f is 3, To find the zeros of f, we set f equal to 0 and solve for x. First, ask yourself, "What am I solving for? What part of the parabola is this? Yes, it's the vertex!

We will need to use the vertex formula and I will need to know the y coordinate of the vertex because it's asking for the height. Now that I know that I need to use the vertex formula, I can get to work. Just as simple as that, this problem is solved. Let's not stop here. Let's take this same problem and put a twist on it. There are many other things that we could find out about this ball!

Projectiles - Example 2 Same problem - different question. How long did it take for the ball to reach the ground?

Now, we've changed the question and we want to know how long did it take the ball to reach the ground. What ground, you may ask.

The problem didn't mention anything about a ground. Let's take a look at the picture "in our mind" again. Do you see where the ball must fall to the ground. The x-axis is our "ground" in this problem. What do we know about points on the x-axis when we are dealing with quadratic equations and parabolas? Yes, the points on the x-axis are our "zeros" or x-intercepts. This means that we must solve the quadratic equation in order to find the x-intercept. Let's solve this equation. I'm thinking that this may not be a factorable equation.

So, what's our solution?

Hopefully, you agree that we can use the quadratic formula to solve this equation. The first time doesn't make sense because it's negative. This is the calculation for when the ball was on the ground initially before it was shot. This actually never really occurred because the ball was shot from the cannon and was never shot from the ground. Therefore, we will disregard this answer. The other answer was 2.

## Need Help Solving Those Dreaded Word Problems Involving Quadratic Equations?

Therefore, this is the only correct answer to this problem. Ok, one more spin on this problem. What would you do in this case? How long does it take the ball to reach a height of 20 feet? Yes, this problem is a little trickier because the question is not asking for the maximum height vertex or the time it takes to reach the ground zerosinstead it it asking for the time it takes to reach a height of 20 feet.