1)|a| = √3²+0²+4² = √25 = 5
|b| = √2²+x²+1² = √(x²+5)
2)a•b = |a|•|b|•cos45°
3•2+0•x+4•1 = 5/√2 √(x²+5)
5/√2 √(x²+5) = 10|•√2/5
√(x²+5) = 2✓2
√(x²+5) = √8
x²+5 = 8
x² = 3
x = ±√3
