9514 1404 393
Answer:
(x, y) = (4, 5)
Step-by-step explanation:
Equating the expressions for y gives ...
-1/4x +6 = x +1
5 = 5/4x . . . . . . . add 1/4x-1
4 = x . . . . . . . . . . multiply by 4/5
y = x +1 = 4 +1
y = 5
The solution is (x, y) = (4, 5).
Answer:
<em>Cathy was born in 1980 and she was 18 years old in 1998</em>
Step-by-step explanation:
<u>Equations</u>
This is a special type of equations where all the unknowns must be integers and limited to a range [0,9] because they are the digits of a number.
Let's say Cathy was born in the year x formed by the ordered digits abcd. A number expressed by its digits can be calculated as
In 1998, Cathy's age was
And it must be equal to the sum of the four digits
Rearranging
We are sure a=1, b=9 because Cathy's age is limited to having been born in the same century and millennium. Thus
Operating
If now we try some values for c we notice there is only one possible valid combination, since c and d must be integers in the range [0,9]
c=8, d=0
Thus, Cathy was born in 1980 and she was 18 years old in 1998. Note that 1+9+8+0=18