Correct Answer - B
`(b)` Since one root is `3`, let
`f(x)=(x-3)(ax+b)`
`implies f(x)=ax^(2)+(b-3a)x-3b`……….`(1)`
Given, `f(-1)+f(2)=0`
`implies (a+(3a-b)-3b)+(4a+2b-6a-3b)=0`
`implies 2a-5b=0`
`implies (b)/(a)=(2)/(5)` ………..`(2)`
Now, product of roots `=(-3b)/(a)=-3((2)/(5))`
since one root...