Question

(5x-2y)(3x+5y)-(2.5x-3y)(4x+8y)

Answer 1

$= 15 {x}^{2} + 25xy - 6xy - 5 {y}^{2} - (10 {x}^{2} + 20xy - 12xy - 24 {y}^{2} ) = 15 {x}^{2} + 25xy - 6xy - 5 {y}^{2} - 10 {x}^{2} - 8xy + 24 {y}^{2} = 5 {x}^{2} + 11xy + 19 {y}^{2}$