Question

Using completing the square to solve for x in the equation (x-12)(x+4)=9

Answer 1

Answer:

x = 4 + √73

Step-by-step explanation:

The given equation is ( x-12 ) ( x + 4 ) = 9

We will solve the equation first.

( x - 12 ) ( x + 4 ) = 9

x( x+4 ) - 12 ( x + 4 ) = 9 [ Distributive property ]

x² + 4x - 12x - 48 = 9

x² - 8x - 48 = 9

x² - 8x - 48 - 9 = 0

x² - 8x - 57 = 0

[ x² - 2 (4x) + 16 ] - 57 - 16 = 0

(x - 4)² - 73 = 0

(x - 4)² = 73

( x-4 )² = √73

x = 4 + √73

x = 4 + √73 is the answer.

Answer 2

Hello!

You can multiply (x-12) and (x+4)

x * x = x^2
x * 4 = 4x
-12 * x = -12x
-12 * 4 = -48

Now we have

x^2 - 8x - 48 = 9

Subtract 9 from both sides

x^2 - 8x -57 = 0

Use the quadratic formula

This give use the answer of

x = 4 +$\sqrt{72}$

Hope this helps!