Question

已知x乘(x减1)减(x的平方减y)等于负4,求(2分之x的平方加y的平方)减xy的值

Answer 1

x(x-1)-(x²-y)=-4
x²-x-x²+y=-4
y-x=-4
x-y=4

所以原式=(x²-2xy+y²)/2
=(x-y)²/2
=4²/2
=8

Answer 2

x(x-1)-(x²-y)=-4
x²-x-x²+y=-4
y-x=-4
x-y=4
所以原式=(x²-2xy+y²)/2
=(x-y)²/2
=4²/2
=8

Answer 3

1、
原式=(1-√2)/[-√6(1-√2)]-√2(3-√3)/(3+√3)(3-√3)
=-√6/6-(3√2-√6)/6
=(-√6-3√2+√6)/6
=-√2/2

2、
原式=[(√3 -√2)+(√2 -1)]/(√3 -√2)(√2 -1)
=(√3 -√2)/(√3 -√2)(√2 -1)+(√2 -1)/(√3 -√2)(√2 -1)
=1/(√2 -1)+1/(√3 -√2)
=√2+1+√3+√2
=2√2+1+√3