Nice job on that second one Melody !!!
There may be some factoring trick for the first, but I would have probably taken Melody's approach and used the Factor Theorem, realizing that there can be no positive real roots because all the linear terms in the original question would be > 0. And multiplying these together and adding a "+15" to them could never give us "0."
The expansion of the original question is x^4 + 16X^3 + 86x^2 +176x + 120, and the factorization of this is, indeed, (x+2) (x+6) (x^2 + 8x + 10)
Using "p/q," the first root ... (-2)... could be found pretty easily...and after some synthetic division, the resulting polynomial would be ... x^3 + 14x^2 + 58x + 60......and the next rational roots that would come to mind to "test" would be -3, -4, -5 and -6. And, as Melody found, -6 is the correct one.
Then, we would use synthetic division again to reduce the polynomial to x^2 + 8x + 10.... and this polynomial has no rational zeroes. (But it does have two "real" roots!!)
Again...good job, Melody !!! Gin and tonics really DO help one's math skills.....(it's an "inside" joke !!!)
I propose a "toast".........

