Алгебра 7 класс N 399,400 на фотографии ниже

N399 1. х²(х+2у)-х-2у=х²(х+2у)-(х+2у)=(х+2у)(х²-1)=(х+2у)(х-1)(х+1) 2. а³-5а²-4а+20=а²(а-5)-4(а-5)=(а-5)(а²-4)=(а-5)(а-2)(а+2) 3. а²-b²+2a(a+b)²=(a-b)(a+b)+2a(a+b)=(a+b)(3a-b) 4. 2(x-y)²+3(x²-y²)=2(x-y)²+3(x-y)(x+y)=(x-y)(2+3x+2y) N400 1. x³+y³+2xy(x+3)=(x+3)(x²-xy+y²+2xy)=(x+3)(x²+xy+y²) 2. a³-b³+5a²b-5ab²=(a-b)(a²+ab+b²)+5ab(a-b)= (a-b)(a²+5ab+b²) 3. 8a³+6a²+3a+1=(2a+1)(4a²+2a+1)+3a(2a+1)=(2a+1)(4a²+5a+1) 4. x³+y³+2x²-2xy+2y²=(x+y)(x²-xy+y²)+2(x²-xy+y²)=(x²-xy+y²)(x+y+2) 5. =a(a³+b³)-b(a³-b³)=(a³-b³)(a-b)