Tham KY's answer to Ethan Ow Yong's Secondary 4 A Maths question.
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Date Posted:
7 years ago
How do u get the 4πr tho
Second derivative... Do differentiation on dV/dr to get the second derivative, you will get -4(pi)r...
Oh ok. To find whether isit more than 0, u juz sub any value to r right. Or must be a specific value?
Must sub the r wanted, not any value.
I did not sub in this case because since the r wanted is positive r (radius cannot be negative), -4(pi)r is definitely negative since pi is a positive constant.
You may sub the r and show the second derivative is less than zero, else must state the statement.
I did not sub in this case because since the r wanted is positive r (radius cannot be negative), -4(pi)r is definitely negative since pi is a positive constant.
You may sub the r and show the second derivative is less than zero, else must state the statement.
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