Question

What number must you add to complete the square? x2-20x=17A. 100B. -10C.-100D. 10

Answer 1

To complete the square:
1) Move the "non X" term to the right:
(Already done)
2) Divide the equation by the coefficient of X² which in this case is 4
(Already done)

then:

• take the coefficient of X
-20

• divide it by 2
-10

• square that number
100

• then add it to both sides of the equation.


So, the answer is A 100

Source:
http://www.1728.org/quadr2.htm

Answer 2

Answer:

The number is 100

A is correct

Step-by-step explanation:

Given: $x^2-20x=17$

We need to make completing square at left side.

Rule: We add a number " take half of the coefficient of x and then square it"

Coefficient of x = 20

Half of 20 = 10

Square of 10 = 100

So, we will add 100 both sides make completing square.

Now we make completing square to add 100

$x^2-20x=17$

Add 100 both sides

$x^2-20x+100=17+100$

Now we will factor left side perfect square

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

$(x-10)^2=117$

$(x-10)^2$ is completing square or perfect square.

Hence, The number is 100