Answer this please please

x is less than -3

Step-by-step explanation:

3x^2+9x<0

x^2+3x<0

x(x+3)<0

x+3<0

x<-3

(n^3 - n)

= n(n-1)(n+1)

since it is divisible by 3 and 2 ,because it is a multiple 3 consecutive number

if, n-1 is odd then n+1 is also odd, then it is a multiple of 9

but if, n-1 is even then n+1 is also even, then it is a multiple of 4

so, largest multiple = max(9*2, 4*3) = max(18, 12) = 18

a+b=c is your answer