Question

Write the set builder form $A=\{-1,1\}$

• A. $A=\{x:x\text{is a real number}\}$
• B. $A=\{x:x\text{is an integer}\}$
• C. $A=\{x:x\text{is a root of the equation}{x}^2=1\}$
• D. $A=\{x:x\text{is a root of the equation}{x}^2+1=0\}$

Answer 1

The correct option is C $A=\{x:x\text{is a root of the equation}{x}^2=1\}$

Clearly there are two element in the set $A$ which is obtained just by solving the equation $x^2=1$
$\therefore A\text{can be rewritten as in the set builder form}=\{x:x\text{is a root of the equation}{x}^2=1\}$