A为和值时,方程组2X-3y=a+1和x+2y=a的解满足xy均为正数?是何不是和
问题描述:
A为和值时,方程组2X-3y=a+1和x+2y=a的解满足xy均为正数?
是何不是和
答
2x - 3y = a+1x + 2y = a2x - 3y = a+12x + 4y = 2a下面式减上面式子 消 x7y = a -1y = (a-1)/7x = a - 2y = a - 2(a-1)/7 = (5a +2)/7x>0y>05a + 2>0a-1>0a > -2/5a > 1所以 要使 x y 均为正数,则 a > 1...