The average height, , in centimetres, of a boy between the ages of 7 years and 10 years can be represented by a line with equation

where is the age in years. For this line, the gradient is 7.

1. What does this indicate about the heights of boys aged 7 to 10?   (1 mark)
   

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2. Give ONE reason why this equation is not suitable for predicting heights of boys older than 10.   (1 mark)
   

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