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Let predicate P(n) be true if equation i=1ni(i+1)=3n(n+1)(n+2) is true. Keep in mind that P(n) is either true or false. It is not a number. Show that P(1) and P(2) are true. If you cannot do that, make sure that you understand what the equation says. Let P(n) be the the same predicate as in the preceding question. (a) Write down what P(n+1) says. Simplify it. (b) Prove that P(n)P(n+1) for every positive integer n