№1
а) (х+4)² = х²+2х*4+4² = х²+8х+16 б) (3b-с)² = (3b)²-2*3bc+c² = 9b²-6bc+c² в) (2x+5)(2x-5) = 4x²-25 г) (y²-x)(y²+x) = y⁴-x²
№2
a)1/9-а² = 1/9*(1-9а²) = 1/9*(1-3а)(1+3а) б)b²+10b+25 = b²+2b*5+5² = (b+5)²
№3
(a-2b)²+4b(a-b) = a²-4ab+4b²+4ba-4b² = a² -(2/3)² = -4/9
№4
a) 3(1+2xy)(1-2xy) = 3(1-4x²y²) = 3-12x²y² б) (x²-y³)² = (x²)²-2x²y³+(y³)² = x⁴-2x²y³+y⁶ в) (a+b)²-(a-b)² = 2b*2a = 4ab
№5
a) (4x-3)(4x+3)-(4x-1)²=3x = 16x²-9-16x²-8x+1=3x = -8x-3x-8 = -11x-8 = -11x=8 = x= -8/11
б) 16c²-49=0 = 16c²=49 = c=-7/4 , с=7/4