## Rodrigo needs to solve the equation x2 – 4x – 18 = 0 by completing the square. Which pair of steps is the most efficient way to begin?

Question

Rodrigo needs to solve the equation x2 – 4x – 18 = 0 by completing the square. Which pair of steps is the most efficient way to begin?

A. x2 – 4x = 18
x2 – 4x + 2 = 18 + 2

B.x2 – 4x = 18
x2 – 4x + 4 = 18 + 4

C.x2 – 4x = 18
x2 – 4x + 81 = 18 + 81

D.x2 – 4x = 18
x2 – 4x + 16 = 18 + 16

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2 weeks 2021-09-13T06:35:06+00:00 2 Answers 0

B.x2-4x=18

x2-4x+4=18+4

Step-by-step explanation:

When you complete the square your quadratic equation must be written in the standard form which is ax^2+bx+c.

First you are going to want to move your c term to the right (in this case move -18 to the right by adding 18 to both sides). This will get you x^2-4x=18. Now you are going to need to complete the square. To complete the square you divide the number in the bx term (in this case -4) by 2 and then square it. (-2^2=4 since a negative times a negative equals a positive). Now that you have 4 you are going to add it to both sides to get x2-4x+4=18+4.