The sum of the digit of a two digit number is13.The tens digit is 17 less than the spuare of the units digit.What is the original number?
unit digit ... x
tens digit ... y , where x and y are positive integers between 0 and 9
we are told:
x+y = 13
y = x^2 - 17
sub 2nd into 1st:
x + x^2 - 17 = 13
x^2 + x - 30 = 0
(x+6)(x-5) = 0
x = -6, which we must reject
or
x = 5
then y = 8
what was the number ?