We use cookies to personalise content and advertisements and to analyse access to our website. Furthermore, our partners for online advertising receive pseudonymised information about your use of our website. cookie policy and privacy policy.
 
+0  
 
+5
1
693
1
avatar

Helo everyone can someone help me to resolve this ? 

 

If f is a linear model for which f(4) = -3 and f(-4) = 21 

 

1. find f(9) 

 

How do I do that ? Can someone show/ explain it to me ? 

 
 Nov 1, 2015
 #1
avatar+28179 
+5

The equation of a straight line can be written as f(x) = m*x + c where m and c are constants found from the given information as follows:

 

 f(-4) = 21  so  21 = -4*m + c    ...(1)

 f(4)  = -3  so   -3 = 4*m + c     ...(2)

 

Add (1) and (2) term by term to get  21 - 3 = -4m + 4m + c + c  or 18 = 2c so c = 9

 

Put this back into (2) to get  -3 = 4m + 9   so 4m = -12  so m = -3

 

Hence the straight line function is  f(x) = -3x + 9

 

Now simply replace x by 9 to work out what f(9) is.

 Nov 2, 2015

29 Online Users

avatar