Question

Укажите верные равенства:
1) (2a+b)2 = 4a2+b2+4ab
2) (2a-b)2 = 4a2+b2+2ab
3) (x-y)(x+y) = x2 - y2
4) (y - 3x)(3x+y) = 9x2 - y2

Answer 1

$(2a + b) {}^{2} = 4 {a}^{2} + 4ab + b {}^{2}$

1) верно

${(2a - b)}^{2} = 4 {a}^{2} - 4ab + {b}^{2}$

2) не верно

$(x - y)(x + y) = {x}^{2} - {y}^{2}$

3) верно

$(y - 3x)(3x + y) = {y}^{2} - 9 {x}^{2}$

4)не верно