1.

Whats the answer to this

Answer»

Answer:

2

Step-by-step explanation:

We know,

     Equation of a circle are written in the form of

     √{ ( x - x₁ )^2 + ( y - y₁ )^2 } = radius

Here,

⇒ x^2 + y^2 + 4x - 2y = - 1

⇒ x^2 + 4x + y^2 - 2y = - 1

     ADDING 4 to both SIDES :

⇒ x^2 + 4x + 4 + y^2 - 2y = - 1 + 4

     Adding 1 to both sides;

⇒ x^2 + 4x + 4 + y^2 - 2y + 1 = - 1 + 1 + 4

⇒ ( x^2 + 4x + 4 ) + ( y^2 - 2y + 1 ) = 4

      Using a^2 + B^2 + 2ab = ( a + b )^2

                 a^2 + b^2 - 2ab = ( a - b )^2

⇒ ( x + 2 )^2 + ( y - 1 )^2 = 4

⇒ { x - ( - 2  ) }^2 + ( y - 1 )^2 = 2^2

⇒ √[ { x - ( - 2 ) }^2 + ( y - 1 )^2 ] = 2

        Now, this equation is in the form as given above, so radius of the that circle must have been represented by the RHS of this eq.

       Radius = 2


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