Example 2.Solve the equation z2=5. x2 =5 x2-5 =0 (x-V5)(x+V5) =0 =50r-vV5 C ●But what is√5？Well,V5 is the positive real number that square to5. We have "learned"that the positive solution to the equation z2-5 is the positive real number that square to 5 !! So there is a sense of circularity in what we have done here. Same thing happens when we say that i is a solution of x2=-1.Example 2. Solve the equation x 2 = 5. x 2 = 5 x 2 − 5 = 0 (x − √ 5)(x + √ 5) = 0 x = √ 5 or − √ 5 • But what is √ 5 ? Well, √ 5 is the positive real number that square to 5. • We have ”learned” that the positive solution to the equation x 2 = 5 is the positive real number that square to 5 !!! • So there is a sense of circularity in what we have done here. • Same thing happens when we say that i is a solution of x 2 = −1