Step-by-step explanation:
[tex]2 \sqrt{7x} .3 \sqrt{14 {x}^{2} } \\ = 2 \times 3 \sqrt{7x \times 14 {x}^{2} } \\ = 6 \sqrt{7x \times 2 \times 7 {x}^{2} } \\ = 6 \sqrt{2 \times 7 \times 7 \times {x}^{2} \times x } \\ = 6 \times 7 \times x \sqrt{2 \times x} \\ = 42x \sqrt{2x} [/tex]
