已知x-2y=2,2y-3z=2,x+3z=14.求x^2-9z^2的值

已知x-2y=2,2y-3z=2,x+3z=14.求x^2-9z^2的值
已知x-2y=2,2y-3z=2,x+3z=14.求x^2-9z^2的值

已知x-2y=2,2y-3z=2,x+3z=14.求x^2-9z^2的值
(x-2y)+(2y-3z)=x-3z=4
x^2-9z^2=(x+3z)(x-3z)=14x4=56

已知x-2y=2,2y-3z=2,x+3z=14
x²-9z²=56

2y-3z+x+3z=16=2y+x
2y+x+x-2y=2x=18
x=9
y=3.5
z=5/3
所以x^2=81
9z^2=225
81-225=144