Answer: 14s^4 - 7s^2 + 15
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Work Shown:
(12s^4-6s^2+4s)+(6s^4-4s+27)-(4s^4+s^2+12)
12s^4-6s^2+4s+6s^4-4s+27-4s^4-s^2-12
(12s^4+6s^4-4s^4)+(-6s^2-s^2)+(4s-4s)+(27-12)
14s^4-7s^2+0s+15
14s^4-7s^2+15
Note: don't forget to distribute the negative to every term in the last parenthesis