(2х-у)(х+у) (a+b)(2a+3b) (3c+a)(2c-a) (6z-y)(2z-y)
(5x-c)(x-5c)
(4m+3n)(4m+3n)
(3y-2u)(10x-5z)
(10x+3z)(10x-5z)

1) = 5х²-25хс - хс +5с² = 5х² -26хс +5с²2) = 16m² +24mn +9n²3) = 30xy -15yz -20 ux +10uz4) = 100x² - 50xz + 30 xz -15z² = 100 x² -20 xz -15z²