Find the derivative of y = (3x +2)(x^2+5)? How do I do this? Please help. Thanks in advance.
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Two ways to do this:
1. Easiest way is to use the product rule which states if y(x)=f(x)*g(x) then dy(x)=f(x)*dg(x)+g(x)*df(x)
In words it says the derivative of a product of two terms is the derivative of the first term times the second term, plus the first term times the derivative of the second term
So in this case *** dy=3(x^2+5)+(3x+2)(2x) ***
2. Otherwise you can simply multiply out the two polynomials and then differentiate normally:
y = (3x +2)(x^2+5) = 3x^3+15x+2x^2+10
then *** dy= 9x^2+15+4x ***
Notice if you multiply out the result from the first method it equals the result from the second method
1. Easiest way is to use the product rule which states if y(x)=f(x)*g(x) then dy(x)=f(x)*dg(x)+g(x)*df(x)
In words it says the derivative of a product of two terms is the derivative of the first term times the second term, plus the first term times the derivative of the second term
So in this case *** dy=3(x^2+5)+(3x+2)(2x) ***
2. Otherwise you can simply multiply out the two polynomials and then differentiate normally:
y = (3x +2)(x^2+5) = 3x^3+15x+2x^2+10
then *** dy= 9x^2+15+4x ***
Notice if you multiply out the result from the first method it equals the result from the second method
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You need to use the product rule
d/dx [ f(x) g(x) ] = d/dx [f(x)] g(x) + f(x) d/dx [g (x)]
d/dx [f(x)] = 3
d/dx [g(x)] = 2x
Use these value and substitute in to the product formula
3(x^2 + 5) + (3x + 2)(2x) =
3x^2 + 15 + 6x^2 + 4x =
9x^2 + 4x + 15
d/dx [ f(x) g(x) ] = d/dx [f(x)] g(x) + f(x) d/dx [g (x)]
d/dx [f(x)] = 3
d/dx [g(x)] = 2x
Use these value and substitute in to the product formula
3(x^2 + 5) + (3x + 2)(2x) =
3x^2 + 15 + 6x^2 + 4x =
9x^2 + 4x + 15
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y = (3x +2)(x^2+5)
y= 3x(x^2+5) + 2(x^2+5)
y= 3x^3+15x+2x^2+10
y= 3x^3+2x^2+15x+10
y= 3x(x^2+5) + 2(x^2+5)
y= 3x^3+15x+2x^2+10
y= 3x^3+2x^2+15x+10
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