SOLUTION: Hello! I have tried this a million times! My homework is full of this and i don't understand!: √(x-3) = √(x+15)-2 Can you take me through the steps to solve it pleas

Algebra ->  Square-cubic-other-roots -> SOLUTION: Hello! I have tried this a million times! My homework is full of this and i don't understand!: √(x-3) = √(x+15)-2 Can you take me through the steps to solve it pleas      Log On


   



Question 554682: Hello! I have tried this a million times! My homework is full of this and i don't understand!: √(x-3) = √(x+15)-2
Can you take me through the steps to solve it please??

Answer by Edwin McCravy(20054) About Me  (Show Source):
You can put this solution on YOUR website!
√(x-3) = √(x+15)-2
sqrt%28x-3%29 = sqrt%28x%2B15%29 - 2

Square both sides:


[sqrt%28x-3%29]² = [sqrt%28x%2B15%29 - 2]²

[sqrt%28x-3%29]² = [sqrt%28x%2B15%29 - 2][sqrt%28x%2B15%29 - 2]

Use FOIL on the right

[sqrt%28x-3%29]² = [sqrt%28x%2B15%29]² - 2sqrt%28x%2B15%29 - 2sqrt%28x%2B15%29 + 4

[sqrt%28x-3%29]² = [sqrt%28x%2B15%29]² - 4sqrt%28x%2B15%29 + 4


x-3 = x+15 - 4sqrt%28x%2B15%29 + 4

x-3 = x+19 - 4sqrt%28x%2B15%29 

-22 = -4sqrt%28x%2B15%29

Square both sides again:

(-22)² = [-4sqrt%28x%2B15%29]²

484 = 16(x+15)

484 = 16x + 240

244 = 16x 

244%2F16 = x

61%2F4 = x

Now we have to check because sometimes there are 
extraneous (phony) solutions to radical equations:

sqrt%28x-3%29 = sqrt%28x%2B15%29 - 2

sqrt%2861%2F4-3%29 = sqrt%2861%2F4%2B15%29 - 2

Get LCD of 4

sqrt%2861%2F4-12%2F4%29 = sqrt%2861%2F4%2B60%2F4%29 - 2

sqrt%2849%2F4%29 = sqrt%28121%2F4%29 - 2

7%2F2 = 11%2F2 - 2

7%2F2 = 11%2F2 - 4%2F2

7%2F2 = 7%2F2

Edwin