(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 +5с² 2) = 16m² +24mn +9n² 3) = 30xy -15yz -20 ux +10uz 4) = 100x² - 50xz + 30 xz -15z² = 100 x² -20 xz -15z²