A conservative force is given by the function F=Kr2, K is a constant. If potential energy is zero at r=r0, then potential energy at r=∞ is
kr0
k2r0
−kr0
−k2r0
∫dU=−∫F→⋅dr→⇒∫0U dU=−∫0∞ kr2[U]0U∞=−K−1rr0∞⇒U∞−0=K−1∞+1r0U∞=−Kr0