Linear Interpolation: Given a pair of (x1,y1), (x2,y2) and x3 predict (x3,y3)

[Tugdual]

(02-16-2014 02:03 AM)Joe Horn Wrote:  This is not a one-keystroke solution, but I think it works. CAS only.

Example:
(x,y)₁ = (1,5)
(x,y)₂ = (7,17)
(x,y)₃ = (10,?)

subst(lagrange([1,7],[5,17]),x=3) --> 23, answer.

In general: subst(lagrange([x₁,x₂],[y₁,y₂]),x=x₃) --> y₃, where "x" is a literal x.

Can somebody sober verify this? Thanx. I'm currently under the influence of Nyquil.

I looks good to me :-)
Prompt recovery!