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If y=(1+x)(1+x2)(1+x4)y = (1+x)(1+x^2)(1+x^4), then dydx\frac{dy}{dx} at x=−1x = -1 is

Solution

✅ Correct Option: 1

By the product rule, every term except the one in which (1+x)(1+x) is differentiated still contains the factor (1+x)(1+x), which vanishes at x=−1x=-1.

So dydx∣−1=1⋅(1+1)(1+1)=4\frac{dy}{dx}\big|_{-1} = 1\cdot(1+1)(1+1) = 4.

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