2)
(x-1)² - 26= x² - 2 x + 1 - 26 = x² - 2 x - 25 = (x + 5 ) ( x - 5) - 2 x
x² + 2 x y + y² - 81 t²= x ( x + 2 y) + ( y + 9 t ) ( y - 9 t)
sau: ( x + y ) ² - 81 t² = ( x + y + 9 t ) ( x + y - 9 t)
3) b) y³ + y - 6y²- 6= y( y² + 1 ) - 6 ( y² + 1) = ( y² + 1) ( y - 6)
4.Dacă a² - b² =76 și a+b=38 atunci a-b= 2
a² - b² = ( a - b ) ( a + b ) = 76
( a - b ) × 38 = 76
a - b = 76 : 38
a - b = 2
5) x² - 7x +12= x² - 4 x - 3 x + 12 = x ( x - 4) - 3 ( x - 4 ) = ( x - 4 ) ( x - 3)