If x² – 10x + 20 = 0, then find the value of (x – 3)² + 1/(x – 3)²

((99.9 - 20.9)² + (99.9 + 20.9)² )/(99.9 x 99.9 + 20.9 x 20.9) = ?

If (5x + 2)³ + (x – 1)³ + 8(3x – 7)³ = 6(5x + 2) × (x – 1) × (3x – 7), then the value of (5x + 3) is 

Find the value of ‘x’ in the given expression:

(49/16)^x × (64/343)^x-1 = 4/7

If x² = 15x + 1, then find the value of {x³ - (1/x³) }.

A dishonest dealer claims to sell goods at cost price but uses a false weight of 900g instead of 1kg. What is his profit percentage?

If (x – 3) is a factor of (x² + 4qx – 2q), then the value of q is:

{(21/20) + (20/21)}² - {(21/20) - (20/21)}² = ?