k为何值时,方程组4x+3y=60,kx+(k+2)y=60的解满足x>y>0.
问题描述:
k为何值时,方程组4x+3y=60,kx+(k+2)y=60的解满足x>y>0.
答
4x+3y=60(1)kx+(k+2)y=60(2)可得4kx+3ky=60k(3)4kx+(4k+8)y=240(4)(3)(4)两式相减(3k-4k-8)y=60k-240求得y=60(4-k)/(k+8)代入(1)得x=60(k-1)/(k+8)已知x>y>060(k-1)/(k+8)>60(4-k)/(k+8)>0化简得(k-1)/(k+8)>(4-k...