解方程組{(x-2)(y+3)=(x+1)(y-1){(x+1)(y+1)=(x-1)(y+5)

解方程組{(x-2)(y+3)=(x+1)(y-1){(x+1)(y+1)=(x-1)(y+5)


{(x-2)(y+3)=(x+1)(y-1)
{(x+1)(y+1)=(x-1)(y+5)
{xy+3x-2y-6=xy-x+y-1
{xy+x+y+1=xy+5x-y-5
{4x-3y=5(1)
{4x-2y=6(2)
(1)+(2)
-y=-1
y=1
4x=5+3y
4x=5+3
4x=8
x=2
方程組的x=2,y=-1



2011*1999和998*1002用平方差計算
要這兩道題的過程我有點不太熟悉。。


2011=2010+11999=2010-1所以2011×1999=(2010+1)×(2010-1)=2010²;-1²;=4040099---------------------------998=1000-21002=1000+2998x1002=(1000-2)×(1000+2)=1000²;-2²;=999996…