= & gta+b = 1
1/a+ 1/b =(a+b)/(ab)= 1/(ab)
When a=b= 1/2, the minimum value 1/a+ 1/b is reached.
Answer: b
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2y = -x+3 (write a straight line equation passing through two points first)
2^x+8/2^x =(2^.5x-sqrt(8)/2^-.5x)^2+4 sqrt(2)
The minimum value of 2 x+8/2 x is 4sqrt(2) if and only if (2.5x-sqrt (8)/2-.5x) 2.
Answer: b