а. (2x-7y)^2 + (3x +4y)^2 - (3x+y)(3x-y)= (4x^2 - 28xy + 49y^2) + (9x^2 + 24xy + 16y^2) - (9x^2 - y^2)= 4x^2 - 28xy + 49y^2 + 9x^2 + 24xy + 16y^2 - 9x^2 + y^2= 4x^2 + 9x^2 - 9x^2 - 28xy + 24xy + 49y^2 + 16y^2 + y^2= 4x^2 + 24xy + 64y^2
б. 5(a-4b)(4b+a) + (a-4b)(-4b+a) + (a+4b)^2= 5(4b + a)(a - 4b) - (4b - a)(4b - a) + (a + 4b)^2= 20b + 5a - 20ab - 5a - 16b + 4b - 4b + a + 16b^2= -20ab + 20b - 16b - a + 4b + 16b^2= -20ab + 4b + 4b + 16b^2= -20ab + 8b + 16b^2
а. (2x-7y)^2 + (3x +4y)^2 - (3x+y)(3x-y)
= (4x^2 - 28xy + 49y^2) + (9x^2 + 24xy + 16y^2) - (9x^2 - y^2)
= 4x^2 - 28xy + 49y^2 + 9x^2 + 24xy + 16y^2 - 9x^2 + y^2
= 4x^2 + 9x^2 - 9x^2 - 28xy + 24xy + 49y^2 + 16y^2 + y^2
= 4x^2 + 24xy + 64y^2
б. 5(a-4b)(4b+a) + (a-4b)(-4b+a) + (a+4b)^2
= 5(4b + a)(a - 4b) - (4b - a)(4b - a) + (a + 4b)^2
= 20b + 5a - 20ab - 5a - 16b + 4b - 4b + a + 16b^2
= -20ab + 20b - 16b - a + 4b + 16b^2
= -20ab + 4b + 4b + 16b^2
= -20ab + 8b + 16b^2