Slope math question?

Question

Write(if possible, a point slope form) an equation of the line that has an x intercept of 3 and passes throught (1,8).

Answer 1

f(x)=-4x+12

Answer 2

y-8=3(x-1) is the point slope form

The 3 is m, or the slope

Answer 3

Let the equation of the line be -

y  =  m x  + c

x-intercept means it intersects the x-axis at a point whose x-coordinate is = 3. Naturally its y-coordinate = 0. Hence this problem reduces to -  find equation of a straight line passing through points ( 3, 0 ) and ( 1, 8 ).

Using formula -

y - y1  =  [( y2 - y1 ) / ( x2 - x1 ) ] ( x - x1 )

=>  y  -  0  =  [ ( 8 - 0 ) / ( 1 - 3 )] . ( x - 3 )

=>  y  =  8 / (- 2 ) .  ( x - 3 )

=>  y  =  - 4 ( x - 3 )

=>  y  =  - 4x  + 12 .......................... Required Result

=>  y  =  ( - 4 ) x  +  12

Slope in this case is = ( - 4 )

Dr. P.K.Tandon