Pascals triangle and binomial theory $(1+x)^n$ expansion

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I have a question that I can solve quite nicely with the binomial theorem; however, I am required to use pascals triangle for a lower level course:

In the expansion of $(1+x)^n$ the first three terms are $1$, $-18$, and $144$. Determine the values of $x$ and $n$.

Answer: $x=-2$, $n=9$

But I don't know how to solve this using pascals triangle!

Thanks