Question

A quadratic equation is shown below:

x2 + 18x + 76 = 0

Which of the following is the first correct step to write the above equation in the form (x - p)2 = q, where p and q are integers?
A. Add 9 to both sides of the equation
B Add 5 to both sides of the equation
C. Subtract 5 from both sides of the equation <---- My answer
D. Subtract 9 from both sides of the equation

Answer 1

I think this question is about writing the left side of the quadratic as a perfect square trinomial.

Answer 2

x2 + 18x + 76 = 0

Take half the coefficient of the x term, 18, and then square it.

1/2*18 = 9.

9^2 = 81

Answer 3

x2 + 18x + 18 = -76 + 18

Answer 4

Why did you subtract 5 - just wondering.

Answer 5

oh ok I see what you mean (:

Answer 6

My technique is not working. Let's test the options.

Answer 7

ok

Answer 8

form (x - p)2 = q, where p and q are integers

I will try adding 5 to both sides

x2 + 18x + 76 = 0

x2 + 18x + 76 + 5 = 0 + 5

x^2 + 18x + 81 = 5

(x + 9)^2 = 5

Answer 9

oh ok

Answer 10

Yes, but there is a plus where there should be a minus. p and q are integers so the expression could be written as:

(x + (-9))^2 = 5

Answer 11

I don't know about that.

Let's try what you think is correct.

Answer 12

ok (:

Answer 13

x2 + 18x + 76 = 0

x2 + 18x + 76 -5 = 0 -5

x^2 + 18x + 71 = -5

This --> x^2 + 18x + 71 is not a perfect square trinomial so that is not the answer.

Answer 14

oh ok I had a feeling at first that it wasn't

Answer 15

Whatever number is added or subtracted has to turn 76 into a a perfect square.

Answer 16

The only option that does that is this: B Add 5 to both sides of the equation

provided that (x + [-9] )^2 = 5 is an acceptable form for the answer.

I don't see why not because of this: form (x - p)2 = q, where p and q are integers

Answer 17

oh ok yea I agree with completely (;

Answer 18

I was just looking at some similar problems and think that the B Add 5 is correct.

Answer 19

oh ok thank you so much again (:, is it ok if u could help with a few more question if that's ok ?

Answer 20

Okay, post in a new thread and close this one, okay?

Answer 21

ok (: