Question 63640
Try using parentheses to show your problem more clearly:
Is it
1) {{{sqrt(x) + 7 = 4}}}? If this, then write: sqrt(x) + 7 = 4 or is it:
2) {{{sqrt(x+7) = 4}}}? If this, then write: sqrt(x+7) = 4

If it's 1):
{{{sqrt(x) + 7 = 4}}} Subtract 7 from both sides.
{{{sqrt(x) = -3}}} Square both sides.
{{{x = 9}}}
Check:
{{{sqrt(9) + 7 = 4}}} Only the negative 3 (-3) is a valid solution.
{{{-3 + 7 = 4}}}
{{{4 = 4}}}

If it's 2):
{{{sqrt(x+7) = 4}}} square both sides.
{{{x+7 = 16}}} Subtract 7 from both sides.
{{{x = 9}}}
Check:
{{{sqrt(9+7) = 4}}}
{{{sqrt(16) = 4}}} {{{4 = 4}}} Only the positive 4 (+4) is a valid solution.
{{{4 = 4}}}