This week in precal 11 

This week in precal 11 I learned how to solve some word questions applications of a parabola. 

 

Here is an example question. 

If the fencing around a rectangular school yard is 80 m, and the area is 225 m, and if the length is x-meters long, what is the width of the fencing?   

 

What we can do now is draw a picture and label the sides.  

We can now create an equation for the sides 

2x+2y=80

Now we isolate the y 

2y=80-2x 

Y=40-x 

So we know the length is x-meters long ,and the width is 40-x meters, we can multiply them together as we know the area is 225 meters 

X(40-x) = 200 

40x –X^2 =200 

Move the like terms around 

X^2-40x-200=0 

We can complete the square 

X^2-20x+400-400-225=0 

(x-20)^2=625 

If we square root both sides we will be left with 

x-20=25 

We can isolate the x 

X=45 

We can put 45 back in the equation to find y 

Y=5