Răspuns
Explicație pas cu pas:
27. x² - 5 x = x ( x - 5)
29. x ( x + 1 ) - x - 1 = x ( x + 1 ) - ( x + 1 ) = ( x + 1 ) ( x - 1 )
31. xy - x - y + 1 = y ( x - 1 ) - ( x - 1 ) = ( x - 1 ) ( y - 1 )
33. 25 x² - 49 = ( 5 x - 7 ) ( 5 x + 7 )
35. x² + 6 x + 9 - y² = ( x + 3 - y ) ( x + 3 + y )
= ( x + 3)² - y² =
= ( x+ 3 - y ) ( x + 3 + y )
37. x² - 5 x + 6 = ( x - 3 ) ( x - 2 )
= x² - 3 x - 2 x + 6 =
= x ( x - 3 ) - 2 ( x - 3 ) =
= ( x - 3 ) ( x - 2 )
39. 2 x² + x - 1 = ( x + 1 ) ( 2 x - 1 )
=2 x² + 2 x - x - 1 =
= 2 x ( x + 1 ) - ( x + 1 ) =
= ( x + 1 ) ( 2 x - 1 )
