1) 2(b^2-c^2)-5(b+c)=2(b-c)(b+c)-5(b+c)=(b+c)(2b-2c-5)2) a² + 2ab +b² - c²=(a+b)^2-c^2=(a+b+c)(a+b-c)3) x² - 2xy +y² - z²=(x-y)^2-z^2=(x-y-z)(x-y+z).
1) 2(b^2-c^2)-5(b+c)=2(b-c)(b+c)-5(b+c)=(b+c)(2b-2c-5)
2) a² + 2ab +b² - c²=(a+b)^2-c^2=(a+b+c)(a+b-c)
3) x² - 2xy +y² - z²=(x-y)^2-z^2=(x-y-z)(x-y+z).
по формуле a² -b² =(a-b)(a+b)
=(x -y -z)(x -y +z)
y^2+20y+100 -9x^2=(y+10)^2-(3x)^2= ( y+10-3x)(y+10+3x)