Question 314766
{{{ graph( 300,300, -5, 5, -10, 10, 3x^4-5x^3-29x^2+45x+18) }}}
Looks like zeros ar x=-3,2,3
Verify using the polynomial,
{{{ 3(-3)^4-5(-3)^3-29(-3)^2+45(-3)+18=243+135-261-135+18=0 }}}
{{{3(2)^4-5(2)^3-29(2)^2+45(2)+18=48-40-116+90+18=0}}}
{{{3(3)^4-5(3)^3-29(3)^2+45(3)+18=243-135-261+135+18=0}}}

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{{{ graph( 300,300, -2, 1, -10, 10, 3x^4-5x^3-29x^2+45x+18) }}}
A closer look reveal x=-1/3 as a possible root.
{{{3(-1/3)^4-5(-1/3)^3-29(-1/3)^2+45(-1/3)+18=1/27-87/27-15+18=0}}}
The four roots are then x={{{-3}}},{{{-1/3}}},{{{2}}},{{{3}}}