Find integers x,y,z such that x^2z+y^2z+4xy=40 and x^2+y^2+xyz=20
Answers
Therefore the values of x = ±√5, y = ±√5, and z = 2.
Given:
x²z+y²z+4xy=40 and x²+y²+xyz=20
To Find:
The values of x, y, and z.
Solution:
The given problem is very simple and can be solved by following this approach.
Given equations: x²z+y²z+4xy=40 and x²+y²+xyz=20
Let equation - 1 be x²z+y²z+4xy=40 and equation - 2 be x²+y²+xyz=20
Let us multiply the second equation with '2' on both sides.
⇒ 2x² + 2y² + 2xyz = 40
Now second equation is subtracted from the first equation.
⇒ ( 2x² + 2y² + 2xyz ) - ( x²z+y²z+4xy ) = 40 - 40
⇒ 2x² + 2y² + 2xyz - x²z - y²z - 4xy = 0
⇒ 2x² - x²z + 2y² - y²z + 2xyz - 4xy = 0
⇒ x² ( 2 - z ) + y² ( 2 - z ) + 2xy ( z - 2 ) = 0
⇒ x² ( 2 - z ) + y² ( 2 - z ) - 2xy ( 2 - z ) = 0
⇒ ( 2 - z ) ( x² + y² - 2xy ) = 0
⇒ ( 2 - z ) ( x - y )² = 0
⇒ ( 2 - z ) = 0 or ( x - y )² = 0
⇒ z = 2 or x = y
Substitute z = 2 and x = y in equation 1,
⇒ x²z+y²z+4xy=40
⇒ ( x² × 2 ) + ( x² × 2 ) + 4x.x=40
⇒ 2x² + 2x² + 4x² = 40
⇒ 8x² = 40 ⇒ x² = 40/8 = 5 ⇒ x = ±√5
∴ x = y = ±√5
Therefore the values of x = ±√5, y = ±√5, and z = 2.
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