Question 1199217
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The work you did is fine.  But if the textbook answers are -2, -1, 1, and 2, then your original polynomial is not right.<br>
{{{(x+2)(x-2)(x+1)(x-1)=(x^2-1)(x^2-4)=x^4-5x^2+4}}}<br>
It looks as if you started with the wrong polynomial.<br>