Question

упрастите выражение (3х-у)(3х+у)+5у^2-9х^2

Answer 1

$(3x-y)(3x+y)+5y^2-9x^2 =9x^2-y^2 + 5y^2 - 9x^2 =-y^2 + 5y^2 \ =4y^2.$