Observe that
6x3+13x2+6x=x(6x2+13x+6)=x(2x+3)(3x+2)
8x3+6x2−9x=x(8x2+6x−9)=x(2x+3)(4x−3),
2x3+3x2=x2(2x+3).
Here we can find the HCF of any two polynomials and then use it to find the HCF of all the three, For example, x(2x+3) is the HCF of 6x3+13x2+6x and 2x3+3x2. Now HCF of x(2x+3) and 8x3+6x2−9x is simply x(2x+3). Therefore the HCF of three polynomials is x(2x+3)