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