Write the expression (4x -2)•6(2x +7)in the standard form of a quadratic expression

(4x - 2) x (12x +42)  (I distributed the 6 over the 2x and the 7)

Using the FOIL method
First terms  (in each parenthesis) 4x  times 12 x = 48x²
Outer terms  4x times 42 = 168x
Inner terms    -2  times 12 x = -24x
Last terms -2 times 42 = -84

So we have 48x² + 168x + 168x - 24x -84
Finally combine like terms:

48x² + 144x - 84    There's your quadratic expression