The function shown in the graph is f(x)

Checking zeros
1.x⁴-2x²+5x+6 =0
x=1,   1-2+5+6= 0, 10=0 false , not first one
2.  x³-2x²-5x+6 =0     correct answer
x=1 ,   1-2-5+6=0,  0=0   true
3.  x³-2x²+5x+6 =0
x=1,  1³-2*1²+5*1+6 =0, 1-2+5+6=0,  10=0 false , not third one
4. -x⁴-2x²+5x+6 =0
x=1, -1-2+5+6 =0, 8=0 false, not this one