SOLUTION: Let g be a linear function such that g(-1)= -3 and g(-4)= 12 Find an equation for g(x) Thank you in advance!

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Question 787462: Let g be a linear function such that g(-1)= -3 and g(-4)= 12
Find an equation for g(x)
Thank you in advance!
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +g%28x%29+=+m%2Ax+%2B+b+
where +m+ = slope and +b+ = intercept at +x+=+0+
given:
+g%28-1%29+=+m%2A%28-1%29+%2B+b+
(1) +-3+=+-m+%2B+b+
------------------
+g%28-4%29+=+m%2A%28-4%29+%2B+b+
(2) +12+=+-4m+%2B+b+
-------------------
Subtract (2) from (1)
(1) +-3+=+-m+%2B+b+
(2) +-12+=+4m+-+b+
+-15+=+3m+
+m+=+-5+
and, since
(1) +-3+=+-m+%2B+b+
(1) +-3+=+-%28-5%29+%2B+b+
(1) +-3+=+5+%2B+b+
(1) +b+=+-8+
-------------
+g%28x%29+=+-5x+-+8+
-----------------
check:
+g%28-4%29+=+-5%2A%28-4%29+-+8+
+g%28-4%29+=+20+-+8+
+g%28-4%29+=+12+
OK
You can check +g%28-1%29+