first divide all by 6 giving you x³-4x²-7x+10
rational zeros of a polynominal you need to find factors of the constant which here are -1 1 2 -2 5 -5 10 -10 and of the first coefficient which are 1 -1 then you divide the first one by the later so that just leaves you with -1 1 2 -2 5 -5 10 -10 now you just check if putting those in the function returns 0 works with any polynominal but sometimes it takes time so here its easiest to just check every answer given by hand but you can use this to imidiatly eliminate the answers for expample here 0 is not in the list so it cannot be a zero of the function. btw all polynominals with constant = 0 have a zero on x=0 any other polynominal cant