I have the below:
r1 = Sum[2*b0*b1*Subscript[x, i], {i, 1, n}] + Sum[b1^2*Subscript[x, i]^4, {i, 1, n}]
I understand that
$\sum _{i=1}^n 2 b_0b_1 x_i+\sum _{i=1}^n b_1^2 x_i^4=2b_0b_1\sum _{i=1}^n x_i+b_1^2\sum _{i=1}^n x_i^4$
However, I do not know how to make Mathematica recognize this. i.e. how to factor the constants $b_0$ and $b_1$ out of the series.
Is there a way to do this?
