+0  
 
+1
4290
4
avatar

suatu fungsi dengan rumus f(x)=ax+b jika f(4)=5 dan f(-2)= -7 , maka tentuka rumus fungsi f(x)?

 Apr 15, 2017
 #2
avatar+128079 
+2

Translation......we wish to write the equation of a line in the form y = mx + b given the points (4, 5)  and (-2, -7)

 

First.....find the slope  =   [subtract y's in some order] / [ subtract x's in the same order]

 

So we have

 

[ -7 - 5] / [ -2 - 4]  =  -12/ -6    = 2

 

And using either point ....the point-slope form becomes

 

y = 2(x - 4) + 5  simplify

 

y = 2x - 8  + 5

 

y = 2x  - 3

 

 

 

cool cool cool

 Apr 15, 2017
edited by CPhill  Apr 15, 2017
 #3
avatar+14865 
+1

suatu fungsi dengan rumus f(x)=ax+b jika f(4)=5 dan f(-2)= -7 , maka tentuka rumus fungsi f(x)?

 

 

A function f(x) = ax + b.    If  f(4) = 5 and  f(-2) = -7, then the function is f(x) = ?

 

 

 

\( f (x) = ax + b\)

\( f (4) = a\cdot 4 + b=5\)

\(a=\frac{5-b}{4}\)

\( f (-2) = -2\cdot a + b=-7\)

\(a=\frac{-7-b}{-2}\)

 

\(\frac{-7-b}{-2}=\frac{5-b}{4}\)

\(-28-4b=2b-10\)

\(6b=-18\\\color{blue}b=-3\)

 

\(a=\frac{5-b}{4}\\a=\frac{5+3}{4}\)

\(a=2\)

 

\(\large f(x)=2x-3\)

 

laugh  ! Thank you C.

 Apr 15, 2017
edited by asinus  Apr 15, 2017
edited by asinus  Apr 15, 2017
edited by asinus  Apr 15, 2017
edited by asinus  Apr 15, 2017
 #4
avatar+128079 
+1

Notice asinus, that  for  (4,5) , y =  -x + 9    is correct

 

But....for   (-2, - 7)    we have that   f(-2)  =  - (-2) + 9   =  11    which is incorrect

 

 

cool cool cool 

 Apr 15, 2017

3 Online Users

avatar