Advertisements
Advertisements
Question
If xm . yn = (x + y)m+n, prove that `"dy"/"dx" = y/x`
Advertisements
Solution
Given that: xm . yn = (x + y)m+n
Taking log on both sides
log xm . yn = log (x + y)m+n ......[∵ log xy = log x + log y]
⇒ log xm + log yn = (m + n) log (x + y)
⇒ m log x + n log y = (m + n) log (x + y)
Differentiating both sides w.r.t. x
⇒ `"m" * "d"/"dx" log x + "n" * "d"/"dx" log y = ("m" + "n") "d"/"dx" log (x + y)`
⇒ `"m" * 1/x + "n" * 1/y * "dy"/"dx" = ("m" + "n") * 1/(x + y) (1 + "dy"/"dx")`
⇒ `"m"/x + "n"/y * "dy"/"dx" = ("m" + "n")/(x + y) * (1 + "dy"/"dx")`
⇒ `"m"/x + "n"/y * "dy"/"dx" = ("m" + "n")/(x + y) + ("m" + "n")/(x + y) * "dy"/"dx"`
⇒ `"n"/y * "dy"/"dx" - ("m" + "n")/(x + y) * "dy"/"dx" = ("m" + "n")/(x + y) - "m"/x`
⇒ `("n"/y - ("m" + "n")/(x + y))"dy"/"dx" = ("m" + "n")/(x + y) - "m"/x`
⇒ `(("n"x + "n"y - "m"y - "n"y)/(y(x + y)))"dy"/"dx" = (("m"x + "n"x - "m"x - "m"y)/(x(x + y)))`
⇒ `(("n"x - "m"y)/(y(x + y))) "dy"/"dx" = (("n"x- "m"y)/(x(x + y)))`
⇒ `"dy"/"dx" = ("n"x - "m"y)/(x(x + y)) xx (y(x + y))/("n"x - "m"y)`
⇒ `"dy"/"dx" = y/x`
Hence proved.
APPEARS IN
RELATED QUESTIONS
Differentiate the function with respect to x.
`(x + 1/x)^x + x^((1+1/x))`
Differentiate the function with respect to x.
(log x)x + xlog x
Differentiate the function with respect to x.
`x^(xcosx) + (x^2 + 1)/(x^2 -1)`
Find `bb(dy/dx)` for the given function:
xy + yx = 1
Find `bb(dy/dx)` for the given function:
xy = `e^((x - y))`
If cos y = x cos (a + y), with cos a ≠ ± 1, prove that `dy/dx = cos^2(a+y)/(sin a)`.
Evaluate
`int 1/(16 - 9x^2) dx`
If `"x"^(5/3) . "y"^(2/3) = ("x + y")^(7/3)` , the show that `"dy"/"dx" = "y"/"x"`
Solve the following differential equation: (3xy + y2) dx + (x2 + xy) dy = 0
If `log_10((x^3 - y^3)/(x^3 + y^3))` = 2, show that `dy/dx = -(99x^2)/(101y^2)`.
If y = `x^(x^(x^(.^(.^.∞))`, then show that `"dy"/"dx" = y^2/(x(1 - logy).`.
If x = esin3t, y = ecos3t, then show that `dy/dx = -(ylogx)/(xlogy)`.
If x = log(1 + t2), y = t – tan–1t,show that `"dy"/"dx" = sqrt(e^x - 1)/(2)`.
If x = sin–1(et), y = `sqrt(1 - e^(2t)), "show that" sin x + dy/dx` = 0
If x = `(2bt)/(1 + t^2), y = a((1 - t^2)/(1 + t^2)), "show that" "dx"/"dy" = -(b^2y)/(a^2x)`.
If y = log (log 2x), show that xy2 + y1 (1 + xy1) = 0.
If y = A cos (log x) + B sin (log x), show that x2y2 + xy1 + y = 0.
If y = log [cos(x5)] then find `("d"y)/("d"x)`
If y = 5x. x5. xx. 55 , find `("d"y)/("d"x)`
If x7 . y5 = (x + y)12, show that `("d"y)/("d"x) = y/x`
lf y = `2^(x^(2^(x^(...∞))))`, then x(1 - y logx logy)`dy/dx` = ______
If y = tan-1 `((1 - cos 3x)/(sin 3x))`, then `"dy"/"dx"` = ______.
`lim_("x" -> 0)(1 - "cos x")/"x"^2` is equal to ____________.
If y `= "e"^(3"x" + 7), "then the value" |("dy")/("dx")|_("x" = 0)` is ____________.
Given f(x) = `log((1 + x)/(1 - x))` and g(x) = `(3x + x^3)/(1 + 3x^2)`, then fog(x) equals
If `log_10 ((x^3 - y^3)/(x^3 + y^3))` = 2 then `dy/dx` = ______.
If `log_10 ((x^2 - y^2)/(x^2 + y^2))` = 2, then `dy/dx` is equal to ______.
Find `dy/dx`, if y = (sin x)tan x – xlog x.
What is logarithmic differentiation?
Which is the derivative of \[\sqrt{\frac{(x-3)(x^2+4)}{3x^2+4x+5}}\]?
What condition must be ensured for an expression inside logarithm?
