1 x²-10x+21=0⇒x1+x2=10 U x1*x2=21⇒x1=3 u x2=7 2x²-15x+7=0 D=225-56=169 x1=(15-13)/4=1/2 U x2=(15+13)/4=7 (x²-10x+21)/(2x²-15x+7)=(x-3)(x-7)/[2(x-1/2)(x-7)]=(x-3)/(2x-1) 2 a)x²+13x+42=(x+6)(x+7) x1+x2=-13 U x1*x2=42⇒x1=-6 U x2=-7 b)не льзя разложить,т.к.D<0 корней нет 3 y²-7y+10=(y-5)(y-2) y1=y2=7 U y1*y2=10⇒y1=2 U y2=5 y²-3y-10=(y-5)(y+2) y1+y2=3 U y1*y2=-10⇒y1=-2 U y2=5 1)(y+5)/[(y-5)(y-2)]-(y-2)/[(yy+2)(y-5)]=(y²+7y+10-y²+4y-4)/[(y-5)(y²-4)]= =(11y+6)/[(y-5)(y²-4)] 2)(11y+6)/[(y-5)(y²-4)]*(y²-4)/(11y+6)=1/(y-5)
x²-10x+21=0⇒x1+x2=10 U x1*x2=21⇒x1=3 u x2=7
2x²-15x+7=0
D=225-56=169
x1=(15-13)/4=1/2 U x2=(15+13)/4=7
(x²-10x+21)/(2x²-15x+7)=(x-3)(x-7)/[2(x-1/2)(x-7)]=(x-3)/(2x-1)
2
a)x²+13x+42=(x+6)(x+7)
x1+x2=-13 U x1*x2=42⇒x1=-6 U x2=-7
b)не льзя разложить,т.к.D<0 корней нет
3
y²-7y+10=(y-5)(y-2)
y1=y2=7 U y1*y2=10⇒y1=2 U y2=5
y²-3y-10=(y-5)(y+2)
y1+y2=3 U y1*y2=-10⇒y1=-2 U y2=5
1)(y+5)/[(y-5)(y-2)]-(y-2)/[(yy+2)(y-5)]=(y²+7y+10-y²+4y-4)/[(y-5)(y²-4)]=
=(11y+6)/[(y-5)(y²-4)]
2)(11y+6)/[(y-5)(y²-4)]*(y²-4)/(11y+6)=1/(y-5)