1.Joe puts up another string of balloons across his driveway. Brenda remembers that their son Brad drives a really tall SUV and worries whether the truck will be able to fit under the balloon arch. Joe figures the arch is described by the function y=-0.4x^2+10, whereis the height (in feet) of the archfeet from the center of the driveway.

If Joes SUV is 6.4 feet tall, how wide can it be and still fit under the arch?

I tried figuring this out myself and I got 5. This is my work:

0=-0.4x^2+10

10=-0.4x^2

25=x^2

5=x

But when I typed the answer in, it was wrong.Help

2.During the birthday party, Joes grandchildren want to know how old he is. Joe, unwilling to volunteer this information directly, gives them a riddle: If I multiply my age when I was 20 years younger with my age when I am 6 years older, I get 5760.

How old is Joe?

I have no idea how to set this up, and the video tutorials are no help. please help.

3.Joe is fascinated by complex numbers and the fact that even if a quadratic equation has no real solution, it will always have a complex solution.Joe has discovered a quadratic equation with unreal solutions.

List the non real solutions of the equation below:

2x^2-4x+4

I tried this one two. But my final step I get is 4+-square root of -16 divided by 4. Which I know that any negative roots there are no real solutions. The correct answer is 1+I,1-i. Can you please help me see or explain how they got this?