I am working on finding the area of a solid object. I have 4 points that I need to calculate a cubic equation from. I have tried relentlessly but to no avail I always get the wrong answer. The four points are;(0,2.7) (0.5, 2.9) (1,3.2) (1.9, 3.4) Using excel, the formula should be; -0.24728x^3 + 0.57093x^2 + 0.17636x + 2.7 If anyone can provide working out on how you got the equation it would be much obliged! No matrices please just substitution.