Question

This is Adele's solution for the equation x^2 + 8x - 9 = 0 Step 1 x^2 + 8x - 9 = 0 Step 2 x^2 + 8x = 9 Step 3 ( x + 4 )^2 = 25 Step 4 x + 4 = 25 or x + 4 = - 25 Step 5 x = 21 or x = - 29. Where did Adele make her mistake. Show all of your work. ​

Answer 1

The mistake was in step one when she added the 9 to both sides

x^2 + 8x - 9 = 0
__ + __ = 8 (b)
__ • __ = -9 (a•c)
blanks = -1 and 9
(x - 1)(x + 9)
Solve for x in each one
x = 1 or -9

Answer 2

The mistake was in step 1.  Here is how to correctly solve the equation:

x² - 8x – 33 = 0

(x - 11) (x + 3) = 0

x – 11 = 0

x +3 = 0

x = 11 and x = -3