Help: Extrapolation with a nonlinear curve?

Hi everybody,

I have two vectors:

x=10^5*[1.1950 4.0436 7.5822  ]
y=[2.3620 4.3620 6.3620]

y=f(x) is a polynomial curve.

I want to find y-value at x = 1.0465*10^9 I tried to extrapolate with fit('pchip') but I couldn't get the result I desired.

May I know how to do it?

Thanks.