Main post link -> http://pibyzero.blogspot.in/2013/05/q.html
Q. A natural number is greater than three times its square root by 4. Find the number.
let, the number be x.
hence according to the condition- x = 3√x + 4
x-4 = 3√x
x² - 8x + 16 = 9x
x² - 17x + 16 = 0
(x-16)(x-1) = 0
x = 16 or x = 1
But when the negative value of square root of 16 and that positive of 1 is taken the equation is not satisfied. WHY ?????????????? Where is the mistake ?