а)
f(x) =3x⁴ - 1 ;
f( -x) =3*(-x)⁴ - 1 =3x⁴ - 1 = f(x) → четная .
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б)
f(x) =5x³ - 2x ;
f( -x) =5*(-x)³ - 2*(-x) =-5x³ +2x =-(5x³ -2x) = - f(x) → нечетная .
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в)
f(x) =(x²+1) / 3x ;
f(-x) = ((-x)²+1) / 3*(-x) = (x²+1) /- (3x) = -(x²+1) / 3x → нечетная .