Find the proper subsets of {x:x2−9x−10=0}
{x:x2−9x−10=0}x2−9x−10=0⇒ x2−10x+x−10=0⇒ x(x−10)+1(x−10)=0⇒ (x−10)(x+1)=0∴ Either x−10=0 or x+1=0⇒ x=10 ⇒ x=−1∴ Given set={−1,10}∴ Proper subsets of this set =ϕ,{−1},{10}
Find the number of proper subsets of A = {1,2,3,4,5,9,12,14}