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Let 
y=(x^(2)+2x)/(4-5x).
What is the value of 
(dy)/(dx) at 
x=2?
Choose 1 answer:
(A) 
-(4)/(3)
(B) 
(1)/(9)
(c) 
-(6)/(5)
(D) 
-(2)/(3)

Let y=x2+2x45x y=\frac{x^{2}+2 x}{4-5 x} .\newlineWhat is the value of dydx \frac{d y}{d x} at x=2? x=2 ? \newlineChoose 11 answer:\newline(A) 43 -\frac{4}{3} \newline(B) 19 \frac{1}{9} \newline(c) 65 -\frac{6}{5} \newline(D) 23 -\frac{2}{3}

Full solution

Q. Let y=x2+2x45x y=\frac{x^{2}+2 x}{4-5 x} .\newlineWhat is the value of dydx \frac{d y}{d x} at x=2? x=2 ? \newlineChoose 11 answer:\newline(A) 43 -\frac{4}{3} \newline(B) 19 \frac{1}{9} \newline(c) 65 -\frac{6}{5} \newline(D) 23 -\frac{2}{3}
  1. Differentiate Function: Differentiate the function yy with respect to xx. We have y=x2+2x45xy = \frac{x^2 + 2x}{4 - 5x}. To find dydx\frac{dy}{dx}, we need to use the quotient rule for differentiation, which is v(u)u(v)v2\frac{v(u') - u(v')}{v^2}, where uu is the numerator and vv is the denominator of the function.
  2. Identify uu and vv: Identify uu and vv and their derivatives.\newlineLet u=x2+2xu = x^2 + 2x and v=45xv = 4 - 5x. Then, the derivatives are u=d(u)dx=2x+2u' = \frac{d(u)}{dx} = 2x + 2 and v=d(v)dx=5v' = \frac{d(v)}{dx} = -5.
  3. Apply Quotient Rule: Apply the quotient rule.\newlineUsing the quotient rule, dydx=(45x)(2x+2)(x2+2x)(5)(45x)2\frac{dy}{dx} = \frac{(4 - 5x)(2x + 2) - (x^2 + 2x)(-5)}{(4 - 5x)^2}.
  4. Simplify Expression: Simplify the expression.\newlinedydx=[8x10x2+810x][5x210x]1640x+25x2\frac{dy}{dx} = \frac{[8x - 10x^2 + 8 - 10x] - [-5x^2 - 10x]}{16 - 40x + 25x^2}.\newlinedydx=10x2+8x+8+5x2+10x1640x+25x2\frac{dy}{dx} = \frac{-10x^2 + 8x + 8 + 5x^2 + 10x}{16 - 40x + 25x^2}.\newlinedydx=5x2+18x+81640x+25x2\frac{dy}{dx} = \frac{-5x^2 + 18x + 8}{16 - 40x + 25x^2}.
  5. Plug in x=2x = 2: Plug in x=2x = 2 into the simplified expression of dydx\frac{dy}{dx}.
    dydx\frac{dy}{dx} at x=2x = 2 is 5(2)2+18(2)+81640(2)+25(2)2\frac{-5(2)^2 + 18(2) + 8}{16 - 40(2) + 25(2)^2}.
    dydx\frac{dy}{dx} at x=2x = 2 is 5(4)+36+81680+100\frac{-5(4) + 36 + 8}{16 - 80 + 100}.
    dydx\frac{dy}{dx} at x=2x = 2 is x=2x = 211.
    dydx\frac{dy}{dx} at x=2x = 2 is x=2x = 244.
    dydx\frac{dy}{dx} at x=2x = 2 is x=2x = 277.

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