What's the value of x?

Question

If f is a linear function and f(-2)=11, f(5)=-2, and f(x)=4.3, what's the value of x?

Answer 1

A = (-2,11)   B = (5,-2)    C = (x, 4.3) are all points on the line.

So, slope AB = slope AC

 

     (-2-11)/(5-(-2)) = (4.3-11)/(x-(-2))

 

                 -13/7 = -6.7/(x+2)

 

                  -13(x+2) = -46.9

 

                  -13x - 26 = -46.9

 

                          -13x = -20.9

 

                            x = 209/130 ≈ 1.61