2 * ( 3a + 7 ) * ( 3a-1) =2(9a²- 3a + 21a -7 )=18a²+36a-14
-3 * ( -4a -4 ) * ( 5a - 2 ) = -3 *(-20a²+8a -20a +8) = 60a²+36a-24
- ( 6x -3 ) * ( 4x + 3 ) =- (24x²+ 18x - 12x - 9) = - 24x ² - 6x+9
- ( 5x + 2 ) * ( - 3 x + 1 ) =-(-15x² +5x - 6x +2 )= 15x² +x -2