1) 25а^2-64b^2 = (5a-8b)(5a+8b)
2) 169a^2-c^2= (13a-c)(13a+c)
3) (5y-4x)^2 = 25y^2-2×5y×4x+16x^2 =25y^2-40xy+16x^2
1) 25а^2-64b^2 = (5a-8b)(5a+8b)
2) 169a^2-c^2= (13a-c)(13a+c)
3) (5y-4x)^2 = 25y^2-2×5y×4x+16x^2 =25y^2-40xy+16x^2