A set of blocks contains blocks of heights 1,2, and 4 centimeters. Imagine constructing towers of piling blocks of different heights directly on top of one another. (A tower of height 6 cm could be obtained using six 1-cm blocks, three 2-cm blocks, one 2-cm block with one 4-cm block on top... etc) Let t be the number of ways to construct a tower of height n cm using blocks from the st ( assume an unlimited supply of blocks of each size). Required:
Find a recurrence relation for t1,t2,t3...

In studies about new medicines, researchers usually give one group of patients the medicine that is designed to treat an illness. They give another group of patients a placebo, which is taken the same way as the medicine but does not actually contain the ingredients of any medicine. Different medicines are tested in different experiments, but the placebos usually contain the same non-medical ingredients. If both groups of patients are healed, then researchers cannot be sure whether the medicine caused improvement, but if the group given the medicine is healed while the group given the placebo remains ill, researchers can conclude that the medicine causes the illness to go away.

In medical experiments, which group receives placebos?

the experimental group

the control group

both the experimental and control groups

neither the experimental nor control group

Explanation:

answerthey protect the head and neck in rear impacts;