28.
a) (n⁵ + 11n⁴) · m – (n⁵ + 11n⁴)(m – 1)
Открываем скобки:
mn⁵ + 11mn⁴ – mn⁵ + 11mn⁴ – n⁵ – 11n⁴ = 22mn⁴ – n⁵ – 11n⁴ = 11mn⁴ – n⁵.
б) (x + 13)(11 – x) – (x – 6)(x + 2)
Так же открываем скобки:
11x + 143 – x² – 13x = –x² – 2x + 143 = x² + 2x – 143
Дискриминант:
x² + 2x – 143 = 0
D = 2² – 4 · (–143) = 4 + 572 = 576 = 24²
x₁ = 
= 
= 11;
x₂ = 
= 
= –13.
ax² + bx + c = a(x – x₁)(x – x₂)
x² + 2x – 143 = (x – 11)(x + 13).
29.
а) 3y – 6 – y² + 2y = 0
–y² + 5y – 6 = 0
y² – 5y + 6 = 0
D = (–5)² – 4 · 6 = 25 – 24 = 1
x₁ = 
= 3;
x₂ = 
= 2.
б) (2x – 3)(1 – 3x) = (2 – 6x)(x – 8)
Открываем скобки:
2x – 6x² + 3 + 9x = 2x – 16 – 6x² + 48x
6x² – 6x² + 11x – 48x – 2x = –3 – 16
–39x = –19
39x = 19
x = 
.