Letting n = 3 in the defining equation an = 3an−1 − an−2, you have a 3 = 3a 2 − a 1 = 3(3) − 4 = 9 − 4
= 5. Letting n = 4 in the defining equation an = 3 an−1 − an−2, you have a 4 = 3a 3 − a 2 = 3(5) − 3 =
15 − 3 = 12. Letting n = 5 in the defining equation, you have a 5 = 3a 4 − a 3 = 3(12) − 5 = 36 − 5 =
31.11 . B
Solve the equation for y. You have
and y = −1. ThenNotice that incorrect choice (A), −1, is the value of y. The question requires finding the value
of .Here is a second way to solve this. The equation of the question stem is .
The right side of the equation is 5 times the left side. Factoring 5 out of the right side of this
equation, you have . When a number equals 5 times itself, the number
must be 0. Thus, .12 . A
13 . C
The graph of the function y = −cos x has y = −1 at x = 0; y increases to 0 at , Y continues
increasing until it is 1 at x = π, then y decreases to 0 at , and y continues decreasing