Math
posted by Forward 27 on .
A student used points (150,80) and (50,30) but wrote the equation y=5x + 0.5. What mistake did the student make?

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