Answer:
Step-by-step explanation:
[tex]3x^4=\boxed{3}\cdot\boxed{x}\cdot\boxed{x}\cdot x\cdot x\\\\15x^3=\boxed{3}\cdot5\cdot\boxed{x}\cdot\boxed{x}\cdot x\\\\21x^2=\boxed{3}\cdot7\cdot\boxed{x}\cdot\boxed{x}\\\\GCF\bigg(3x^4,\ 15x^3,\ 21x^2\bigg)=\boxed3\cdot\boxed{x}\cdot\boxed{x}=3x^2[/tex]
