Under which circumstances is the incomplete beta function equal to Gauss hypergeometric function

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$$B_y(x, z)= \frac{y^x}x2F1(x, 1 − z; 1 + x; y)$$

Note: 2F1 represents the Gauss hypergeometric function. I had trouble around its notation here.

I have this relationship between an incomplete beta function and a Gauss hypergeometric function. However, when I plot the two sides of the relationship for 0<y<1 and x>z>0, the graphs are not the same. Instead, they diverge. I then fixed y at y=0.5 and varied x and then z, but the graphs are still different. This then begs the question, when is this relationship true?

Urgent help will be highly appreciated. Thanks in advance.

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The incomplete beta function definition that is expressed as a Gauss hypergeometric function:

$$B_y(x,z)=\int_0^yt^{x-1}(1-t)^{z-1}dt=\frac{y^x}x2F1(x,1-z;1+x;y)$$

The incomplete beta function as defined in MATLAB: $$I_y(x,z)=\frac{1}{B(x,z)}\int_0^yt^{x-1}(1-t)^{z-1}dt=\frac{B_y(x,z)}{B(x,z)}$$

What this means is that I was actually using $I_y(x,z)$ in place of $B_y(x,z)$ in MATLAB.