1980 AHSME Problem 24

For some real number r, the polynomial 8x^3-4x^2-42x+45 is divisible by (x-r)^2. Which of the following numbers is closest to r?

\text{(A)} \ 1.22 \qquad \text{(B)} \ 1.32 \qquad \text{(C)} \ 1.42 \qquad \text{(D)} \ 1.52 \qquad \text{(E)} \ 1.62

Full credit goes to MAA for authoring these problems. These problems were taken on the AOPS website.