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An equation of the line tangent to y=x^3+3x^2+2 at its point of inflection is

For the rule of 78, for a 12-month period, the last term in the sequence is 12 and the series sums to 78. for an 10 month period, the last term is and the series sum is . for a 15 month period, the last term is and the series sum is . for a 20 month period, the last term is and the series sum is

Find the solution set of this inequality. enter your answer in interval notation using grouping symbols. |8x-4| ≤ 12