# Solve sqrt (x+ a) = x −7 when a=-1

#### rebo1984

##### New member
Hi,

If a = -1, what is the solution set of the equation sqrt (x+ a) = x −7

{5}
{10}
{5, 10}
No solution

(5,10) correct?

Thanks

#### MarkFL

Staff member
Hi,

If a = -1, what is the solution set of the equation sqrt (x+ a) = x −7

{5}
{10}
{5, 10}
No solution

(5,10) correct?

Thanks
What do you get when you substitute each potential solution into the original equation?

#### rebo1984

##### New member
What do you get when you substitute each potential solution into the original equation?
It works out.

#### MarkFL

Staff member
It works out.
Let's try $$x=5$$:

$$\displaystyle \sqrt{5-1}=5-7$$

$$\displaystyle 2=-2$$

Is this true?

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