yang bisa tolong dibantu no 8

|a pada b| = 2√6 = √24

a pada b
= (a . b) b / |b|²
= (2+x+2) (2 1 1) / [√(2²+1²+1²)]²
= (4+x) (2 1 1) / 6
= ((8+2x)/6 (4+x)/6 (4+x)/6)

|a pada b|
= √[((8+2x)/6)²+((4+x)/6)²+((4+x)/6)²]
= √[(64+4x²+16+x²+16+x²)/36]
= √[(96+6x²)/36]
√24 = √((96+6x²)/36)
24 = (96+ 6x²)/36
96+6x² = 24.36
96+6x² = 864
6x² = 864-96
x² = 768 /6
x = √128 = 8√2

|a| = √(1²+(8√2)²+2²)
= √(1+128+4) = √133
|b| = √(2²+1²+1²)
= √6

Cos α= a.b / |a||b|
Cos α= 2 + 8√2 + 2 / √133*√6
Cos α= 4 + 8√2 / √798