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Answer:
0.67 cm/s
Step-by-step explanation:
The area of a square is given by :
....(1)
Where
x is the side of a square

Differentiating equation (1) wrt t.

When A = 81cm², the side of the square, x = 9 cm
Put all the values,

So, the length of the side of a square is changing at the rate of 0.67 cm/s.
If f(1) =5-2(1)
F(2)=5-2(2)