[tex]a)2x \times x - 2x \times 5 + 3x - 3 \times 5 = 2 {x}^{2} - 7x - 15[/tex]
[tex]b)41 \times 2x + 41 \times 3y - 5y \times 2x - 5y \times 3y = 82x + 123y - 10xy - 15 {y}^{2} [/tex]
[tex]c)3 \times 68 = 204[/tex]
[tex]d) {a}^{2} - {(b - 1)}^{2} = {a}^{2} - ( {b}^{2} - 2b + 1) = {a}^{2} - {b}^{2} + 2b - 1[/tex]
