What number must be added to the expression below to complete the square x2-20x?

100

Step-by-step explanation:

I believe you meant x^2 - 20x; " ^ " denotes exponentiation.

Take half the coefficient of the x term (which in this problem is -20).  We get -10.  Now square this, obtaining 100.

Adding 100 to x^2 - 20x "completes the square."

100.

Step-by-step explanation:

We have been given an expression . We are asked to find the number that must be added to the expression to complete the square.

We know that a perfect square is in form .

To complete a square we need to add the half the square of b that is .

Upon looking at our given expression we can see that b is equal to 20, so would be:

Therefore, we must add 100 to our given expression to complete the square.

let soccer = x and golf = y

part a

1st equation: x + y = 125

2nd equation: x = y +45

part b

replace x in the 1st equation with the 2nd one:

y + 45 + y = 125

simplify:

2y + 45 = 125

subtract 45 from each side:

2y = 80

divide both sides by 2:

y = 80/2

y = 40

she plays golf for 40 minutes.

part c

no because she plays soccer for 45 minutes longer than golf 40 +45 =   85 minutes, not 80 minutes.