Question

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

Answer 1

$(3x-7y)(2x+3y)-(4x-5y)(3x+y)\\\\=3x\cdot2x+3x\cdot3y-7y\cdot2x-7y\cdot3y-...\\\\...-(4x\cdot3x+4x\cdot y-5y\cdot3x-5y\cdot y)\\\\=6x^2+9xy-14xy-21y^2-(12x^2+4xy-15xy-5y^2)\\\\=6x^2-5xy-21y^2-(12x^2-11xy-5y^2)\\\\=6x^2-5xy-21y^2-12x^2+11xy+5y^2\\\\=-6x^2+6xy-16y^2$