Question:
Write the following sets in roster from:
J = {x : ϵ R and x2 + x – 12 = 0}.
Solution:
The given equation is:
$x^{2}+x-12=0$
$\Rightarrow x^{2}+4 x-3 x-12=0$
$\Rightarrow x(x+4)-3(x+4)=0$
$\Rightarrow(x-3)(x+4)=0$
$\Rightarrow x-3=0$ or $x+4=0$
$\Rightarrow x=3$ or $x=-4$
therefore, the solution set of the given equation can be written in roaster form as {3, -4}
So, J = {3, -4}