b) Tính giá trị A khi x = căn bậc hai 2
Giải thích
b) Khi x = 2
A=(2)2−2+12−1
=2−2+12−1=3−22−1
x+y=33x−4y=2⇔x=3+y3x−4y=2⇔x=3+y3(3+y)−4y=2⇔x=3+y9+3y−4y=2⇔x=3+yy=7⇔x=10y=7
b) Khi x = 2
A=(2)2−2+12−1
=2−2+12−1=3−22−1
x+y=33x−4y=2⇔x=3+y3x−4y=2⇔x=3+y3(3+y)−4y=2⇔x=3+y9+3y−4y=2⇔x=3+yy=7⇔x=10y=7