Question

упростите выражение (3x-7y)(2x+3y)-(4x-5y)(3x+y)

Answer 1

$(3x-7y)(2x+3y)-(4x-5y)(3x+y)\\=3xcdot2x+3xcdot3y-7ycdot2x-7ycdot3y-...\\...-(4xcdot3x+4xcdot y-5ycdot3x-5ycdot y)\\=6x^2+9xy-14xy-21y^2-(12x^2+4xy-15xy-5y^2)\\=6x^2-5xy-21y^2-(12x^2-11xy-5y^2)\\=6x^2-5xy-21y^2-12x^2+11xy+5y^2\\=-6x^2+6xy-16y^2$