Question 41439
 
  The answers are as under:
  1) {{{(y^2-13y+36)}}} = (y-4)(y-9) Answer

  2) {{{(x^2+9x+18)}}} = (x+3)(x+6) Answer.
 
  Just knowing the answers are not sufficient.  You must know to solve such problems.  In such problems, if the co-efficient of the first term is 1, then do as below:
1)  Find out 2 such numbers product of which should be equal to the third term and the sum of the same numbers should be equal to the co-efficient of the second term i.e. middle term.  Here in the first problem it is -4 and -9.
2)  Verify the sum and product equals to the co-efficients of 2nd and 3rd terms respectively. 
3)  Now split up the middle term  with those numbers as in your first example, it -4y and -9y and write it down as {{{y^2-9y-4y+36}}}
4)  Take the first two terms and the last two terms seperately and factorise each. We get {{{y(y-9)-4(y-9)}}} .  Then we take the common factor i.e. (y-9)and factorise as (y-9)(y-4) i.e. taking the co-efficients of the common factor i.e. y and -4.  That's all.  I hope this is clear to you.

gsm