Question

I cannot find these things anywhere in my book, for even an example...

Over two summers, Ray saved $800.00 and $600.00. The polynomial represents his savings at the beginning of the third year, where x is the growth factor. (The interest rate r is x – 1.) What is the interest rate he needs to save $1,650.00 after the third summer?

800x2 + 600x (1 point)
0.1%
10.9%
–285.9%
1.1%

Answer 1

what are those number after (1 point) rewrite the question. if those are potential answers number them or denote them somehow.

Answer 2

this is a goofy way of asking to solve for x in the quadratic
\[ 800 x^2 +600x = 1650 \]
and then find the interest rate r = x – 1
Write r as a percent (i.e. 100*(x-1) will be the answer)

Answer 3

ivan77 those are the possible answer. It's multiple choice.

Answer 4

phi I kind of understand what you put down, but not quite.

Answer 5

The polynomial represents his savings at the beginning of the third year

those words mean that
\[ 800x^2 + 600x\] is a way to calculate his savings at the start of the 3rd year
x is how much the savings grow.

They want you to find x so that the expression equals 1650

Answer 6

So I have to get x by itself?

Answer 7

yes, you have to solve a quadratic equation
800 x^2 +600x = 1650
you can divide by 10 (all terms) to simplify it a bit

\[ 80 x^2 +60 x - 165 =0 \]

Answer 8

I can't find an example of how to solve a quadratic equation in my book...

Answer 9

what are you studying ?

Answer 10

Algebra II

Answer 11

Solving quadratics is a part of Algebra II

Are you allowed a calculator?

Answer 12

See
http://www.khanacademy.org/math/algebra/quadratics/quadratic_formula/v/using-the-quadratic-formula

Answer 13

Imean I'm home schooled I'll do whatever I want. So yes I can use a calculator.

Answer 14

Ok, take a look at the video. It should be helpful.