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If y = emtan-1x, show that (1+x2)d2ydx2+(2x-m)dydx = 0 - Mathematics and Statistics

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Question

If y = `"e"^("m"tan^(-1)x`, show that `(1 + x^2) ("d"^2y)/("d"x^2) + (2x - "m")("d"y)/("d"x)` = 0

Sum

Solution

y = `"e"^("m"tan^(-1)x`    .......(i)

Differentiating w. r. t. x, we get

`("d"y)/("d"x) = "d"/("d"x)("e"^("m"tan^-1x))`

= `"e"^("m"tan^-1x)*"d"/("d"x)("m"tan^-1x)`

= `"e"^("m"tan^-1x)*"m"/(1 + x^2)`

= `("m"y)/(1 + x^2)`    .......[From (i)]

∴ `(1 + x^2)("d"y)/("d"x)` = my

Again, differentiating w. r. t. x, we get

`(1 + x^2)*"d"/("d"x)(("d"y)/("d"x)) + ("d"y)/("d"x)*"d"/("d"x)(1 + x^2) = "m"("d"y)/("d"x)`

∴ `(1 + x^2)*("d"^2y)/("d"x^2) + ("d"y)/("d"x)*2x = "m"("d"y)/("d"x)`

∴ `(1 + x^2) ("d"^2y)/("d"x^2) + (2x - "m")("d"y)/("d"x)` = 0

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Higher Order Derivatives
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Chapter 2.1: Differentiation - Long Answers III

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