The function f(t) = 15,000(0.86)t models the value in dollars of a used car t years after it is purchased. is the function an exponential growth function or an exponential decay function?

/is used for a fraction 1) if x = 2/3 and y = 3/4, what is the value of (x + y) (x/y) expressed as a common fraction? 2) what is the least positive integer greater than 1 that leaves a remainder of 1 when divided by each of 2, 3, 4, 5, 6, 7, 8, and 9? 3) the ponde family's powerjet pumps 420 gallons of water per hour. at this rate, how many gallons of water will it pump in 45 minutes? 4) kim's insurance company pays 80% of the cost of all prescription medication she purchases in a year beyond the first $250 worth of prescriptions. her prescriptions for this year cost a total of $570. how many dollars of this amounts will kim's insurance company pay?

Solve the system of equations. y= 2x y= x^2 - 15

Which shows the correct substitution of the values a,b and c from the equation 1=-2x+3x^2+1