Posted by **Felicia** on Tuesday, October 30, 2012 at 5:13pm.

square root ( 2x+1) +x=7

- algebra -
**Steve**, Tuesday, October 30, 2012 at 5:18pm
√(2x+1) + x = 7

√(2x+1) = 7-x

2x+1 = 49 - 14x + x^2

x^2 - 16x + 48 = 0

(x-12)(x-4) = 0

x = 4 or 12

check:

√(2*4+1)+4 = √9 + 4 = 3+4 = 7

√(2*12+1)+12 = √25 + 12 = 5+12 = 17 BOO!

Why? Because this is true only if we take the -√: -5+12 = 7, but that's not the original equation. Squaring both sides allowed for using + or - √.

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