Problema Solution
A two digit number is such that its tens digit is greater than its unit digit by 4.the two digit number is less than 4 times the product of its digit by 11.find the two digit number.
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Solution
x = tens digit
y = ones digit
x = y + 4
10x + y = 4xy - 11
10(y+4) + y = 4(y+4)y - 11
10y + 40 + y = 4y2 + 16y - 11
4y2 + 5y - 51 = 0
(4y+17)(y-3) = 0
y = -17/4 ==> invalid
y = 3
x = 3 + 4
x = 7
Answer: 73