After 4 years, $3,006 deposited in a savings account with simple interest had grown to a total of $3,967.92. What was the interest rate?

So interest rate is 8% per annum

Step-by-step explanation:

Principal amount = $3,006

Amount at end = $3,967.92

Time = 4yrs

interest money = ($3967.92 - $3006)  

also equal to = 4 * (x/100) * $3,006

Where x is the interest rate per annum

So, 4 * (x/100) * $3,006 = ($3967.92 - $3006)

        x = 8%

So interest rate is 8% per annum

if the eqn of the parabola is f(x) = (x-4)(x+2), we need to mult. this out to find the coordinates of the vertex.

then f(x) = x^2 + 2x - 4x - 8, and f(x) = x^2 - 2x - 8.

one way in which you can find the vertex is to calculate x = -b / (2a).   here, that comes to

        )

x = = 1.   f(1) = 1^2 - 2(1) - 8 = - 9.   vertex is at (1, -9).

        2(1) 

find another point on the curve:   let x=0, for which y=-8.   then (0, -8) is on the curve.   plot the vertex and this point and draw a smooth parabola thru both.

hope this