Given:
x2 + y2 + 2y + 4x + 5 = 0
Concept Used:
The concept of quadratic equation is used
Calculations:
The given equation is
x2 + y2 + 2y + 4x + 5 = 0
To make the equation quadratic for x and y we have to add some values according to the coefficient of x =and y respectively
⇒ The coefficient of x is 4x = 2 × 2 × x
so for x, we have to add square of 2 and subtract square of 2
⇒ The coefficient of y is 2x = 2 × 1 × y
so for x, we have to add square of 1 and subtract square of 1
So, The equation will become
⇒ x2 + y2 + 2y + 4x + 5 + 4 - 4 + 1 - 1 = 0
⇒ x2 + 4x + 4 + y2 + 2y + 1 + 5 - 4 - 1= 0
⇒ (x + 2)2 + (y + 1)2 = 0
On putting the value of x = -2 and y = -1, we get the value 0
⇒ So , x = - 2 and y = -1
The value of x−yx+y=
⇒ x−yx+y=−2−(−1)−2−1=−1−3 = 3
⇒ Hence, The value of the given equation is 3
Alternate Method
x2 + y2 + 2y + 4x + 5 = 0
⇒ x2 + y2 + 2y + 4x + 4 + 1 = 0
⇒ x2 + 4x + 4 + y2 + 2y + 1 = 0
⇒ (x + 2)2 + (y + 1)2 = 0
So, x = -2 and y = -1
Then, x−yx+y= -3/-1 = 3