Объяснение:
Завд. 3 . ( m² - 57 )/( m - 7 ) - 8/( 7 - m ) = ( m² - 57 )/( m - 7 ) + 8/( m - 7 ) =
= ( m² - 57 + 8 )/( m - 7 ) = ( m² - 49)/( m - 7 ) = m + 7 ;
якщо m = 3 , то m + 7 = 3 + 7= 10 .
Завд. 4 . m²/( m - 1 ) + 3mn/( m - 1 ) + ( mn - n²)/( 1 - m ) = m²/( m - 1 ) +
+ 3mn/( m -- 1 ) + ( n² - mn )/( m -- 1 ) = (m² + 3mn + n² - mn )/( m -- 1 ) =
= ( m² + 2mn + n² )/( m -- 1 ) = ( m + n )²/( m - 1 ) .
В - дь : 2 ) ( m + n )²/( m - 1 ) .
