若x2-y2=48,x+y=6,则3x-3y=_.
问题描述:
若x2-y2=48,x+y=6,则3x-3y=______.
答
x2-y2=(x+y)(x-y)=48,
∵x+y=6,
∴x-y=8,
则3x-3y=3(x-y)=3×8=24.
故答案为24.