I don't know where to go with this question:

'Let r be a fixed real number. Show that {1, x + r, (x + r)²} is a basis for R[x]2 (that's meant to be a subscript 2) and find the co-ordinates a0 +a1 +a2x² (integers are also meant to be subscript) with respect to this basis.'

Thanks in advance.