Question

Efectuează:
(0,8x+15)(0,8x-15)+0,36x² =

Ajutati-ma va rog. Dau coroana

Answer 1

(0,8x+15)(0,8x-15)+0,36x² = 

= 0,8² *x²-225+0,36x² =

= (4/5)² *x² -225+0,36x² =

= 16/25x²-225+0,36x² =

= 16/25x² - 225 +9/25x² = x² -225 

Answer 2

In primul rand, aplicam formula (a-b)(a+b)=a²-b² =>(0.8x)² - 15² =>0.8² x x² - 225+ 0,36x² =>Acum il  facem pe 0,8 sub forma de fractie => (4/5)² x x² -225 +0,36x²=> 4²/5² x x² -225 +0.36x² => 16/25 x² - 225 +9/25 x² => x² - 225=> Raspuns final : x² - 225