Answer:
[tex]3x^7+4|x| = 3x^7+4x [if~x\geq 0]\\3x^7+4|x|=3x^7-4x [if~x<0]\\In~both~of~the~cases,~power~of~x~is~a~whole~number.~Therefore,~3x^7+4|x|~is~a~polynomial.[/tex]
