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Let x and y be real numbers such that x^2 + y^2 = 4(x + y). Find the largest possible value of x.

User Petehare
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1 Answer

1 vote

Answer:

The largest possible value of x is 2 + √8

Explanation:

Given;

x² + y² = 4(x + y)

This is an equation of circle

x² + y² = 4x + 4y

x²- 4x + y² - 4y = 0

complete the square by taking half of coefficient of x and y, then add the squares to both sides;

x²- 4x + (-2)² + y² - 4y + (-2)² = (-2)² + (-2)²

factorize

(x - 2)² + (y - 2)² = √8

This circle has its center at (2, 2) with a radius of √8

The largest x-value occurs at the right end of the circle = x value of the center plus the radius = 2 + √8

User Evet
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