Решите уравнение

(5a + 2) (5a-2) - 5a (5a-1) = 21

3 (y+2) kv + (2y-1) kv - 7 (y+3) (y-3) = 28

1) (5a + 2) (5a-2) - 5a (5a-1) = 21

1) 25a²-4-25a²+5a=21

5a=25

a=5

2) 3 (y+2) kv + (2y-1) kv - 7 (y+3) (y-3) = 28

a) kv=0

-7 (y+3) (y-3) = 28

y²-9=-4

y²=5⇒y=-√5 y=√5

kv≠0

3kvy+6kv+2kvy-kv-7y²+63-28=0

7y²+5kvy+35+kv=0

D=25k²v²-27 (35+kv) = 25k²v²-27kv-945

1) 25k²v²-27kv-945<0=нет решения

2) 25k²v²-27kv-945=0

y=-5kv/14

3) 25k²v²-27kv-945>0

y1 = (-5kv-√ (25k²v²-27kv-945)) / 14

y2 = (-5kv+√ (25k²v²-27kv-945)) / 14