1.
a) (7a-5ay+9)-(21a-4ay) = 7a-5ay+9-21a+4ay = 9-ay-14a
b) 5x²(2x³-3) = 5x²*2x³-3*5x² = 10x⁵-15x²
2.
a) 20yp - 25y² = 5y * 4p-5y * 5y = 5y(4p-5y)
b) 28e⁵+7e² = 7e² * 4e³ + 7e² = 7e²(4e³+1)
3.
19x-8(x-1) = 15(x+2)
19x-8x+8 = 15x+30
11x-15x = 30-8
-4x = 22
x = -22/4 = -11/2 = -5.5
Ответ: x = -5.5