Answer
$-3x^4-9x^2-x-13$
Work Step by Step
$(6x^4-20x^2-x+3)-(9x^4-11x^2+16)=6x^4-20x^2-x+3-9x^4-(-11x^2)-16=(6-9)x^4+(-20+11)x^2-x+(3-16)=-3x^4-9x^2-x-13$
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