Determine which polynomial is a perfect square trinomial.

49x^2 − 28x + 16
9a^2 − 30a + 25
25b^2 − 45b − 81
16x^2 − 24x − 9

answer: cos [   arcsin (3/5) - arccos (1/2) ] =

step-by-step explanation: × = 3/5 = 0.6--> x = 36.87 and x = 180 - 36.87 = 143.13 deg

cos y = 1/2 --> y = +- 60 deg a. cos (x - y) = cos (143.13 - 60) = cos 83,13  

=

0.12

b. cos (36.87 - 60) = cos (-23.23) = 0.92