If x and y are positive integers such that 6 x 1 4 y = 4 8 ⋅ 4 2 y , what is ( x , y ) ?
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Factoring the exponents, we get 2 x ⋅ 3 x ⋅ 2 y ⋅ 7 y = 2 4 ⋅ 3 1 ⋅ 2 y ⋅ 3 y ⋅ 7 y . Dividing by 7 y and combining equal-base exponents we get 2 x + y ⋅ 3 x = 2 4 + y ⋅ 3 1 + y . Looking at powers of 2, x + y = 4 + y , so x = 4 . Looking at powers of 3, x = 1 + y , so y = 3 . Our ordered pair is ( 4 , 3 ) .
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6 x 1 4 y = 4 8 × 4 2 y
6 x = 4 8 × 3 y
2 x 3 x = 2 4 × 3 × 3 y
2 x − 4 = 3 y + 1 − x
Since both exponents are integers and 2 and 3 are coprimes, therefore the equation above can only stand, when both exponents are zero.
This gives us:
x − 4 = 0 ⇒ x = 4
and
y + 1 − x = 0 ⇒ y + 1 − 4 = 0 ⇒ y = 3
Hence, our answer should be:
( 4 , 3 )