To solve this problem you must apply the proccedure shown below:
1. You have that the the archway is modeled by the equation y=-2x^2+8x and the angle mentioned in the problem is defined by the equation x−2.23y+10.34=0.
2. Therefore, you must susbtitute y=-2x^2+8x into x−2.23y+10.34=0, as below:
x−2.23(-2x^2+8x)+10.34=0
3. When you apply the distributive property, you obtain:
x−2.23(-2x^2+8x)+10.34=0
x+4.46x^2-17.84x+10.34=0
4.46x^2-16.84x+10.34=0
4. When you solve the quadratic equation, you obtain:
x=3 units
Therefore, the answer is the option D: D. 3 units.
