Witaj :)
a]
[tex](7x-5)\cdot(8x+6)=7x\cdot8x+7x\cdot6-5\cdot8x-5\cdot6=\\\\=56x^2+42x-40x-30=\boxed{56x^2+2x-30}[/tex]
b]
[tex](9-k)\cdot(k-9)=9\cdot k-9\cdot9-k\cdot k-k\cdot(-9)=\\\\=9k-81-k^2+9k=\boxed{-k^2+18k-81}[/tex]
c]
[tex](8x+4)\cdot(9x+5)=8x\cdot9x+8x\cdot5+4\cdot9x+4\cdot5=\\\\=72x^2+40x+36x+20=\boxed{72x^2+76x+20}[/tex]
