Question 168292
 [SQRT(x + 7)] - 2[SQRT(x)] =-2
I know x = 9
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The simplest way is to get one radical by itself, then square both sides.
 [SQRT(x + 7)] - 2[SQRT(x)] =-2
{{{sqrt(x+7) = 2sqrt(x) - 2}}}
Now square
{{{x+7 = 4x -8sqrt(x) + 4}}}
Now isolate the other radical
{{{-8sqrt(x) = -3x + 3}}}
Square again
{{{64x = 9x^2 - 18x + 9}}}
{{{9x^2 - 82x + 9 = 0}}}
*[invoke solve_quadratic_equation 9,-82,9]
The onsite solver doesn't do factors correctly if the coefficient of the the x^2 is not 1, but the answers are right, 9 and 1/9.
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How tall is a stack of cube-shaped blocks whose volumes are 375 cubic inches, 648 cubic inches and 1,029 cubic inches? 
A. 10 cubert(3)
B. 6 cubert(3)
C. 3 sqrt(3)
D. 4 sqrt(3)
E. 9 sqt(3)
F. 18 cubert(3)
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I don't know what you mean by that.  More info is needed.