SOLUTION: You can model an arch at your school using the equation y=−0.9(x+3)(x−3)y=−0.9(x+3)(x−3), where xx and yy are measured in feet. The x-axis represents the gr

Algebra ->  Quadratic Equations and Parabolas -> SOLUTION: You can model an arch at your school using the equation y=−0.9(x+3)(x−3)y=−0.9(x+3)(x−3), where xx and yy are measured in feet. The x-axis represents the gr      Log On


   

Question 1071189: You can model an arch at your school using the equation y=−0.9(x+3)(x−3)y=−0.9(x+3)(x−3), where xx and yy are measured in feet. The x-axis represents the ground. Find the width of the arch at ground level.
The width of the arch at ground level is
feet.
Found 2 solutions by josmiceli, MathTherapy:
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
The arch meets with the ground are the values of
+x+ where +y+=+0+
---------------------------------
+y+=+-.9%2A%28+x+%2B+3+%29%2A%28+x+-+3+%29+
--------------------------------
+x+=+-3+
+y+=+-.9%2A%28+-3+%2B+3+%29%2A%28+-3+-+3+%29+
+y+=+-.9%2A0%2A%28+-6+%29+
+y+=+0+
---------------------
+x+=+3+
+y+=+-.9%2A%28+3+%2B+3+%29%2A%28+3+-+3+%29+
+y+=+-.9%2A6%2A0+
+y+=+0+
----------------------
The distance between ( -3, 0 ) and ( 3, 0 )
is +3+-%28-3%29+=+6+
The width of the arch at ground level is 6 ft
-----------------------
Here's the plot of the equation:
+graph%28+400%2C+400%2C+-4%2C+4%2C+-1%2C+10%2C+-.9%2A%28+x+%2B+3+%29%2A%28+x+-+3+%29++%29+

Answer by MathTherapy(10555) About Me  (Show Source):
You can put this solution on YOUR website!

You can model an arch at your school using the equation y=−0.9(x+3)(x−3)y=−0.9(x+3)(x−3), where xx and yy are measured in feet. The x-axis represents the ground. Find the width of the arch at ground level.
The width of the arch at ground level is
feet.
Based on the given equation, x + 3 = 0, and x - 3 = 0, so roots are: - 3, and 3. 

Distance from - 3 to 3 is: 3 - - 3, or 3 + 3, or highlight_green%28matrix%281%2C2%2C+6%2C+feet%29%29.

That's it!!