An elf has a staircase of n stairs to climb. each step it takes can cover either one stair or two stairs. find a recurrence relation for a_n, the number of different ways for the elf to ascend the n-stair staircase. find a recurrence relation for the number or ways the elf in example 2 can climb n stairs if each step covers either one or two or three stairs? how many ways are there for the elf to climb four stairs?

Given the points a(-2, 1) and b(8, 6), find the coordinates of the point c on directed line segment ab, that partitions ab in the ration 2: 3.

Which of the following is the true for f(x) = 5cos

An office supply company conducted a survey before marketing a new paper shredder designed for home use. in the survey, 80 % of the people who tried the shredder were satisfied with it. because of this high satisfaction rate, the company decided to market the new shredder. assume that 80 % of all people are satisfied with this shredder. during a certain month, 100 customers bought this shredder. find the probability that of these 100 customers, the number who are satisfied is 69 or fewer.