Find the value of dy/dx for the given value of x.
a) y = (1 - 2x)(1 + 2x), x = 1/2
y' = 2(1 + 2x) + 2(1 - 2x)
y' = 2 + 4x + 2 - 4x
y' = 4
How do I find the derivative at x = 1/2 if there is no x variable to substitute the x value with? According to my textbook, the answer is -4.
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Textbook Answer: -4
a) y = (1 - 2x)(1 + 2x), x = 1/2
y' = 2(1 - 2x) - 2(1 + 2x)
y' = 2 -4x -2 - 4x
y' = ?