SOLUTION: find an exponential function of the form f(x) = ba^-x + c that has the horizontal asymptote y = 350 and y-intercept 70 and passes through the point (10,300).

Algebra ->  Exponential-and-logarithmic-functions -> SOLUTION: find an exponential function of the form f(x) = ba^-x + c that has the horizontal asymptote y = 350 and y-intercept 70 and passes through the point (10,300).      Log On


   



Question 1194927: find an exponential function of the form f(x) = ba^-x + c that has the horizontal asymptote y = 350 and y-intercept 70 and passes through the point (10,300).
Answer by greenestamps(13200) About Me  (Show Source):
You can put this solution on YOUR website!


f%28x%29=ba%5E%28-x%29%2Bc

(1) For large values of x, a^(-x) goes to zero, so the function is f%28x%29=c. The value of the function approaches 350 for very large values of x, so c=350. The function is

f%28x%29=ba%5E%28-x%29%2B350

(2) When x=0, a^(-x)=1, so the function is f%28x%29=b%2B350. Since f(0)=70,

b%2B350=70
b=-280

The function is

f%28x%29=-280a%5E%28-x%29%2B350

(3) The function value is 300 when x=10.

300=-280a%5E%28-10%29%2B350
280a%5E%28-10%29=50
a%5E%28-10%29=50%2F280=5%2F28
a%5E10=28%2F5=5.6
a=5.6%5E%281%2F10%29 = 1.18800 to 5 decimal places.

ANSWER: The function is

f%28x%29=-280%281.188%29%5E%28-x%29%2B350