b_0(x)

6\cdot b_1(x)

6\cdot b_2(x)

b_3(x)

b0(x) = If[x > 0 ∧ x < 1, 1 - x]
b1(x) = If[x > 0 ∧ x < 1, (((-(x - 1)) * (x - 2)) * x)]
b2(x) = If[x > 0 ∧ x < 1, (((x - 1) * (x + 1)) * x)]
b3(x) = If[x > 0 ∧ x < 1, x]