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and 
are given. For which real numbers 
is 
?
higher than the water level at low tide when at high tide.
years.
units on his mobile phone in January. The mobile operator charges 
for each unit, so he paid 
for the January payment slip. Write down which two variables are interdependent? Specifies the dependent and independent variable. Explain your answer.
. Which equation also describes this dependence:
