Question

Tolong dijawab yah !

Answer 1

A=(2,3,1)
B=(1,0,2)
C=(-1,4,1)

a+b+c = {(2+1-1) , (3+0+4), (1+2+1)} = (2, 7, 4)

2a+3b - c = 2 (2,3,1) + 3(1,0,2) - 1(-1,4,1)
2a+3b - c = (4,6,2) + (3,0,6) -(-1,4,1) = {(4+3+1),(6+0-4),(2+6-1)}
2a+3b - c = (8, 2, 7)

2)
A= (1,2,1) --> |a| = √(1²+2²+1²)= √4= 2
B = (-2,4,2)--> |b| = √(-2)²+(4)²+(2)² = √24 = 2√6

a.b = 1(-2) + 2(4)+ 1(2)= 8

cos α = a.b /|a||b| = 8 /(2)(2√6) = 8/(4√6) = (8√6)/(24) = ¹/₃ √6