One out of Infinity: Interpolating polynomials For this challenge, when given a list of (x,y) points your submission needs to output a polynomial function that goes through all of them.
For example, if your points were [(0,0), (2,5)], you could return y = 2.5*x or y = x + 1/4x^2.

All points passed in will consist only of integers
Two points will never have the same y value
Your function be of the form y = a*x^n + ... b*x^m.   Reducing of terms is allowed.
Constants (the exponent and coefficient) can either be in decimal or fractional form.  Decimals should be accurate to at least 3 decimal places
You should be able to handle an arbitrary number of points
Output must be a string starting with &quot;y=&quot;. Whitespace anywhere in the string is fine.

Test cases
Note, the given output is not the only valid output, just one of the possibilities.
(1,4)                                                    -&gt; y=x+3
(0,0), (1,8)                                             -&gt; y=8x
(0,6), (-1,90)                                           -&gt; y=-84x+6
(6,4), (70,4), (-1,-6)                                   -&gt; y=−10/497x^2+760/497x−316/71
(4,5), (5,6), (6,7)                                      -&gt; y=x+1
(20,1), (-20,1), (0,5), (10, 4), (11,12), (17,4), (2,4)  -&gt; y=488137/10424165400x^6−643187/473825700x^5−87561839/10424165400x^4+550999039/1042416540x^3−21590713027/5212082700x^2+300110420/52120827x+5

This is a code-golf, so make your answers as short as possible in your favorite language!
MATL, 38 bytes
ynq3$ZQ'y=' '%+fx^%i'btn:qP&amp;vYDh1J3-h)

Inputs are an array with the x values and an array with the y values.
Try it online!
y          % Inplicitly take the two inputs, and push another copy of the first
nq         % Get its length minus 1. This is the required polynomial degree.
3$ZQ       % Coefficients of polynomial fitted to those data (`polyfit`)
'y='       % Push this string
'%+fx^%i'  % Push format string for `sprintf`
b          % Bubble up the polynomial coefficients to the top of the stack
tn:qP      % Duplicate and produce [n n-1  ... 0] where n is the polynomial degree.
           % These are the exponents
&amp;v         % Concatenate vertically. This gives a 2D array with the coefficients in
           % the first row and the exponents in the second
YD         % Apply `sprintf` to this array with previous format string. The array
           % is read in column-major order: down, then across
h          % Concatenate 'y=' and formatted string representing the polynomial
1J3-h)     % The string ends in '...x^0'. Remove last three chars to delete this.
           % Implicitly display