Andrew factored the expression 14x^3 -21x^2-7x as 7x (14x^2-21x-7) But when Melissa applied the distributive?

Andrew factored the expression 14x^3 -21x^2-7x as 7x (14x^2-21x-7) But when Melissa applied the distributive law and multiplied out 7x(14x^2-21x-7), she got 98x^3-147x^2-49x; thus, Andrew’s solution does not appear to check. Why is that? Please help Andrew to understand this better. Explain your reasoning and correctly factor the original expression, if possible. If the expression is prime, so state.