A student used points (150,80) and (50,30) but wrote the equation y=5x + 0.5. What mistake did the student make?

Answer 1

Equation of line through two points:

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

In this case :

x1 = 150

y1 = 80

x2 = 50

y2 = 30

so :

y = 80 + [ ( 30 - 80 ) / ( 50 - 150 ) ] * ( x - 150 )

y = 80 + [ ( - 50) / ( - 100) ] * ( x - 150 )

y = 80 + ( 1 / 2 ) * ( x - 150 )

y = 80 + x / 2 - 150 / 2

y = 80 + 0.5 x - 75

y = 0.5 x + 5