Answer:
see explanation
Step-by-step explanation:
The equation of a parabola in vertex form is
y = (x - h)² + k (h, k) are the coordinates of the vertex
Given y = x² + 7x - 5
To express in vertex form use the method of completing the square
add/subtract ( half the coefficient of the x- term )²
y = x² + 2( )x +
-
- 5
y = (x + )² -
-
y = (x + )² -
Hence
a = and b = -
So for this problem, we will be using the exponential equation format, which is y = ab^x. The a variable is the initial value, and the b variable is the growth/decay.
Since our touchscreen starts off at a value of 1200, that will be our a variable.
Since the touchscreen is decaying in value by 25%, subtract 0.25 (25% in decimal form) from 1 to get 0.75. 0.75 is going to be your b variable.
In this case, time is our independent variable. Since we want to know the value 3 years from now, 3 is the x variable.
Using our info above, we can solve for y, which is the cost after x years.
In context, after 3 years the touchscreen will only be worth $506.
