how does (x+9)^2=81 end up to be x=(-18)?

Answer 1

(x+9)^2=81

square root both side
x+9= -9 or 9

x= -9-9 or 9-9

x= -18 or 0

Answer 2

(x+9)^2=81 end up to be x=(-18)?

(x+9)^2=81 end up to be x=(-18)?
Take square root of both sides getting:
x+9 = +/- 9
So x = +/- 9 - 9
x = 0 or x = -18

Answer 3

Solve: (x+9)^2 = 81....

First: expand the terms in parenthesis raised to the 2nd power...

(x+9)(x+9) = 81

*Eliminate parenthesis > use the foiling method...

(x)(x) + (x)(9) + (9)(x) + (9)(9) = 81

x^2 + 9x + 9x + 81 = 81

x^2 + 18x + 81 = 81

Sec: set the equation to "0" > subtract "81" from both sides...

x^2 + 18x + 81 - 81 = 81 - 81

x^2 + 18x = 0

Third: factor the expression > find the least common factor...

x(x + 18) = 0

Fourth: solve the x-variables > set them both to "0"...

a. x = 0

b. x + 18 = 0
*Subtract "18" from both sides...

x + 18 - 18 = 0 - 18
x = - 18

Solutions: 0 and -18

Answer 4

Take the square root of both sides:
(x+9)=9 or x+9= -9

x = 0 or x = -18

Answer 5

(x + 9)^2 = 81

Your first step would be to take the square root of both sides. Note that whenever you take the square root of both sides of an equation, you have to add a "plus or minus", or "+/-"

x + 9 = +/- 9

Now, move the 9 to the right hand side,

x = -9 +/- 9

This means we have two solutions for x.

x = {-9 + 9, -9 - 9}, OR
x = {0, -18}