Question

1. Solve 5x2 = –45x. using compleing the square

Answer 1

First add 45x to both sides and then factor out the 5

Answer 2

\[5(x^2+9x)=0\]

Answer 3

Now complete the square by adding 81/4 inside the parentheses which is really adding 5 times 81/4 so now subtract 405/4 outside the parentheses

Answer 4

\[5(x^2+9x+(\frac{9}{2})^2)-5(\frac{9}{2})^2=0\]

Answer 5

\[5(x+\frac{9}{2})^2=5(\frac{9}{2})^2\]

Answer 6

divide by 5 and then take the square root of both sides.

Answer 7

Then subtract 9/2 from both sides. You will get 0 which is obviously the solution. Why you would be required to solve this equation by completing the square is beyond me.

Answer 8

I agree I would have used an easier method.

Answer 9

5x² = –45x
5x² + 45x = 0
5 (x² + 9x) = 0
5 ( x + 9/2)² = 5 * (9/2)²
->( x + 9/2)² = +/- (9/2)
-> x + 9/2 = 9/2 => x = 0 , x = 9

Answer 10

Oops, x = 0, x = -9