Đáp án:
$1)
a)
A=10000\\
b)
B=42\\
2)
a)
N=300000\\
b)
P=0\\
c)
Q=280\\
d)
R=0\\
e)
S=1820$
Giải thích các bước giải:
$1)
a)
A=x^2-8x-y(8-x)\\
=-x(8-x)-y(8-x)\\
=(8-x)(-x-y)\\
\Rightarrow A(108,-8)=(8-108)(-108+8)=-(-100).(-100)=10000\\
b)
B=xy(x+y)-2x-2y\\
=xy(x+y)-2(x+y)\\
=(x+y)(xy-2)\\
\Rightarrow B=7.(8-2)=7.6=42\\
2)
a)
N=x^2(y-1)-5x(1-y)\\
=x^2(y-1)+5x(y-1)\\
=x(y-1)(x+5)\\
\Rightarrow N(-20,1001)=(-20).(1001-1)(-20+5)=(-20).1000.(-15)=300000\\
b)
P=y^2(x^2+y-1)-x^2-y+1\\
=y^2(x^2+y-1)-(x^2+y-1)\\
=(x^2+y-1)(y^2-1)\\
\Rightarrow P(9;-80)=(9^2-80-1)((-80)^2-1)=0.6399=0\\
c)
Q=x(x-y)^2-y(x-y)^2+xy^2-x^2y\\
=(x-y)^2(x-y)+xy(y-x)\\
=(x-y)\left [(x-y)^2-xy \right ]\\
\Rightarrow Q=7.(7^2-9)=7.40=280\\
d)
R=x^2(x+y)-y^2x-y^3\\
=x^2(x+y)-y^2(x+y)\\
=(x+y)(x^2-y^2)\\
=(x+y)(x+y)(x-y)\\
=(x+y)^2(x-y)\\
\Rightarrow R=(-2017+2017)^2(-2017-2017)=0\\
e)
S=y^3-3y^2-y(3-y)\\
=y^2(y-3)+y(y-3)\\
=y(y-3)(y+1)\\
\Rightarrow S(13)=13.(13-3).(13+1)=13.10.14=1820$
