Question

Answer 1

`@` `\text {Ans}`

`\downarrow`

`c)`

`(2x + 5)(3x - 1) - 6x(x - 3) - 21x`

`= 2x(3x - 1) + 5(3x - 1) - 6x^2 + 18x - 21x`

`= 6x^2 - 2x + 15x - 5 - 6x^2 + 18x - 21x`

`= (6x^2 - 6x^2) + (-2x + 15x + 18x - 21x) - 5`

`= 10x - 5`

`d)`

`(x + y)^2 + (x-y)^2 - 2x^2`

`= x^2 + xy + y^2 + x^2 - xy + y^2 - 2x^2`

`= (x^2 + x^2 - 2x^2) + xy + y^2 - xy +y^2`

`= xy + y^2 - xy + y^2`

`= (xy - xy) + y^2 + y^2`

`= 2y^2`

_____

`@` CT:

`(A+B)^2 = A^2 + 2AB + B^2`

`(A - B)^2 = A^2 - 2AB + B^2`