Answer :
(x+1)(x-2) = x(x-2) + 1(x-2)
= x.x - x . 2 + 1. x - 1 . 2
= x² - 2x + x -2
= x²-x -2
^_^
= x.x - x . 2 + 1. x - 1 . 2
= x² - 2x + x -2
= x²-x -2
^_^
[tex]\mathfrak{solution} :\\\\(x+1)(x-2)\\=x(x-2)+1(x-2)\\=x^{2}-2x+x-2\\=x^{2}-x-2\\\\========================================\\\\\mathfrak{note:}\\\boxed{(x+a)(x-b)=x(x-b)+a(x-b)}[/tex]
