Question

Сравните с нулем значение данных выражений (y-3)(y-5), (3-y)(y-5), (5-y)(3-y), если известно, что : а) y<3 б) y>5 в) 3

Answer 1

А) y<3, тогда
y-3<0, y-5<0
(y-3)(y-5)>0

3-y>0, y-5<0
(3-y)(y-5)<0

5-y>0, 3-y>0
(5-y)(3-y)>0

б) у>5
 y-3>0, y-5>0
(y-3)(y-5)>0

3-y<0, y-5>0
(3-y)(y-5)<0

5-y<0, 3-y<0
(5-y)(3-y)>0

в) 3<y<5
 y-3>0, y-5<0
(y-3)(y-5)<0

3-y<0, y-5<0
(3-y)(y-5)>0

5-y>0, 3-y<0
(5-y)(3-y)<0