Question

Consider the following three equations:

linear: y=20x+300
Quadratic: y=5x^2
Exponential: y=10(1.4)^x
use the equations to answer the following questions. Support your answers with work.
1. At an x-value of 11, which equation has the largest y-value?
2. what is the smallest integer value of x for which the value of the exponential equation is greater than the values of both the linear and quadratic functions?

Answer 1

1.

y = 20(11) + 300 = 520

y = 5(11)(11) = 605

y = 10(1.4)^11 = 404.96

hence the quadratic formula - y = 5x^2 has the largest y-value

2.

y = 20 (14) + 300 = 580

y = 5 (14) (14) = 980

y = 10(1.4)^ 14 = 1111.20 > this is greater than both equations above

14 is the smallest value of x for which the value of the exponential equation is greater than the values of both the linear and quadratic functions

Explanation:

Answer 2

1. Quadratic

2. x = 14

Explanation:

1. At x = 11

linear: y=20(11) + 300 = 520

Quadratic: y=5× 11² = 605

Exponential: y=10(1.4)¹¹ = 404.956517

2. 10(1.4^x) > 20x + 300

1.4^x > 2x + 30

1.4^x - 2x - 30 > 0

Using trial method:

x > 11

10(1.4^x) > 5x²

1.4^x - 0.5x² > 0

Using trail method:

x > 13

The smallest positive integer which satisfies both inequalities is 14