the unit digit of a 2-digit number is 1 less than the square of the tens digit.the sum of the number and the number formed by reversing its digits is 121.find the original number.
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maths f4
2011-01-04 5:44 am
回答 (1)
2011-01-04 5:50 am
✔ 最佳答案
unit digit = xtens digit = y
x = y^2 - 1
10y + x + 10x + y = 121
11y + 11x = 121
y + x = 11
y^2 - 1 = 11 - y
y^2 + y - 12 = 0
(y + 4)(y - 3) = 0
y = 3
x = 8
original number = 10y + x = 38
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