If a is a unit vector Ibl = 5 and la + b1 = square root17. determine (-4a - 3b) • (b + 7a)

Answer 1

|a| = 1
|b| = 5
|a+b| = √17
(-4a - 3b) • (7a + b) = -28a•a - 25a•b - 3b•b
= -28 - 15 - 25a•b
= -43 - 25a•b
See what you can do with that, and the definition of a•b