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Which of the following are true about the expansion of * 1 poll'rt (x + y)3 '1' I. The sum of the power: of x and y in any term is 3. II. The number of terms in the exp union is 9. III. The coefficient of x4y4 is 56. IV. The sum of the numerical coefficients 23. 0 main 0 lllonhr O l,||,l||&|'|u|' 0 \"law