Question

把36写成两个正数的积,当这两个正数取什么值时,它们的和最小? [用人教实验A版高2知识回答]

Answer 1

x*y = 36

y = 36/X

f = X + 36/X

f*X = X*X + 36

X*X - f*X + 36 =0

b*b-4ac>=0

f*f-144>=0

f >= 12

和最小 12

x*x -12*x +36 =0

x = 6

y=36/x = 6