Помогите! 7 класс алгебра

1)

$(2x {}^{2} + 4)(8x {}^{2} - 3) = \\ 16x {}^{4} - 6x {}^{2} + 32x {}^{2} - 12 = 16x {}^{4} + 26x {}^{2} - 12$

2)
$(y {}^{2} - 7)(y {}^{2} + 7) = \\ (y {}^{2} ) {}^{2} - 7 {}^{2} = y {}^{4} - 49$

3)
$(x {}^{2} - 4)(x + 3) = \\ x {}^{2} \times x + 3x {}^{2} - 4x - 4 \times 3 = \\ x {}^{3} + 3x {}^{2} - 4x - 12$

4)
$(2c { }^{2} - c + 6)(c + 5) = \\ 2c {}^{3} + 10c {}^{2} - c {}^{2} - 5c + 6c + 30 = \\ 2c {}^{3} + 9c {}^{2} + c + 30$

5)
$(a - 3)(3a {}^{2} - 5a + 2) = \\ 3a {}^{3} - 5a {}^{2} + 2a - 9a {}^{2} + 15a - 6) = \\ 3a {}^{2} - 14a {}^{2} + 17a - 6$

6)
$(4x + 3)(x + 4) - (3x + 5)(2x + 4) + x(2x + 3) = \\ 4x {}^{2} + 16x + 3x + 12 - (6x {}^{2} + 12x + 10x + 20) + 2x {}^{2} + 3x = \\ 4x {}^{2} + 16x + 3x + 12 - (6x {}^{2} + 22x + 20) + 2x {}^{2} + 3x = \\ 4x {}^{2} + 16x + 3x + 12 - 6x {}^{2} - 22x - 20 + 2x {}^{2} + 3x = - 8$