Question

Let ( x^{2}+18 x+30=z )
( Rightarrow quad z=2 sqrt{z+15} )
( Rightarrow quad t^{2}=4(t+15) )
( Rightarrow quad t^{2}-4 z-60=0 )
( Rightarrow(t-10)(t+6)=0 )
( Rightarrow quad t=10,-6 )
( therefore x^{2}+18 x+30=10 quad ) as ( quad x^{2}+18 x+30=-6 )
( =5 x^{2}+18 x+20=0 quad ) a ( quad x^{2}+18 x+36=0 )
Pdt ( y times sec t=+20 )
Pat. 9 sorts ( =36 )

# 3. Find the product of the real roots of the equation, x2 + 18x + 30 = 21x2 +18x +45

Solution