Answer: The factorised form is
[tex](x-3)(-7x^2+3)[/tex]
Step-by-step explanation:
Since we have given that
[tex]-7x^3+21x^2+3x-9[/tex]
We need to factorise the above expression by grouping:
[tex](-7x^3+21x^2)+(3x-9)\\\\=-7x^2(x-3)+3(x-3)\\\\=(x-3)(-7x^2+3)[/tex]
Hence, the factorised form is
[tex](x-3)(-7x^2+3)[/tex]