Equation of a straight line, y=mx+c where m is the gradient of the line m= change in y∕ change in x=(y2−y1)∕(x2−x1) NOTE: The first coordinate represents the x-axis and the second the y-axis Thus in (−3,5),x=−3 and y=5 ln(6,8),x=6 and y=8 ⇒ The gradient of the line =(8−5)∕(6−−3)=3∕(6+3)=3∕9=1∕3 Use any of the points and the gradient to calculate the value of c Using the point (−3,5) ⇒5=1∕3x−3+c ⇒5=−1+c ⇒5+1=c ⇒c=6 Using the point (6,8) ⇒8=1∕3×6+c ⇒8=2+c ⇒8−2=c ⇒c=6 Hence the equation will be y=1∕3x+6