I need to complete the square, but I still can't get the answer right.

Question

x^2+40x+c

Answer 1

Take 1/2 the coefficient of x and square it (40/2)² =400

Rewrite the equation adding and subtracting 400, (x²+40x+400)+c-400 This can be written as (x+20)² +c-400 from which you can find the roots (x+20)²=400-c by taking+- the square root of both sides and solve for x₁, x₂.

 

Hope this helps

 

Jim

Answer 2

x² + 40x + c

 

x² + 40x + (40/2)²

 

x² + 40x + 20²

 

(x+20)²