4. Найдите значение дроби: 1) (y² − 11y − 26)/(9y + 18) при y = −5; 31; 112; 2) (x² − 18x + 80)/(5x − 50) при x = −12; 8,5; 48.

1) \(\dfrac{y^2-11y-26}{9y+18}=\dfrac{(y-13)(y+2)}{9(y+2)}=\dfrac{y-13}{9}\).

• при \(y=-5\): \(\dfrac{-5-13}{9}=-2\);
• при \(y=31\): \(\dfrac{31-13}{9}=2\);
• при \(y=112\): \(\dfrac{112-13}{9}=11\).

2) \(\dfrac{x^2-18x+80}{5x-50}=\dfrac{(x-10)(x-8)}{5(x-10)}=\dfrac{x-8}{5}\).

• при \(x=-12\): \(\dfrac{-12-8}{5}=-4\);
• при \(x=8.5\): \(\dfrac{8.5-8}{5}=0.1\);
• при \(x=48\): \(\dfrac{48-8}{5}=8\).

Ответ: 1) −2; 2; 11. 2) −4; 0,1; 8.