Find the exact value of the following question:

$$ \sqrt {123×8+2389-1164}=? $$

Find the exact value of the following question:

$$ (13+2\sqrt{5})^2=?\sqrt{5}+189 $$

Find the exact value of the following question:

$$ 8\sqrt{?}÷14×3+9=21$$

Find the exact value of the following question:

$$ 1280÷{2^3} + 1220÷{2^2}-182=?$$

Find the exact value of the following question:

$$ 3{1\over2} × 3 {1\over 7}+ 5{3\over4}÷{46\over3}=?$$

(3x-7)³+(3x-8)³+(3x+6)³=3(3x-7)(3x-8)(3x+6)
Find the value of x ?

If  $$  \left( x^2+{1\over x^2} \right)- \left( x - {1\over 4} \right)- 7 =0 $$ then two value of x are :

In solving a problem, one student makes a mistake in the coefficient of the first degree term and obtains – 9 and – 1 for the roots. Another student makes a mistake in the constant term of the equation and obtains 8 and 2 for the roots. The correct equation was