What is the scientific notation of 0.000487

Which expression is equivalent to (3^2)^-2 a.-81 b.-12 c.1/81 d.1/12

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

Aline passes through 3,7 and 6,9 what equation represents the line