Question 937033


 {{{y^2+10y+k}}} is a perfect square trinomial, 

to find the value of {{{k}}} use {{{10y}}} and recall the rule {{{(a+b)^2=a^2+2ab+b^2}}}; so,in {{{10y}}} we know that {{{b=y}}} and {{{2a=10}}}=>{{{a=5)

using that we have 
 {{{(y^2+10y+_)-_+k}}} 

{{{(y^2+10y+5^2)-25+k}}} 

{{{(y+5)^2-25+k}}} ...=> to have a perfect square trinomial {{{k}}} must be {{{25}}}

{{{(y+5)^2-25+25}}}

{{{(y+5)^2}}}