Problemas
Let f(x)=x^2+9x+20 and g(x)=x^3-4x Find (fg)(x) and ((f)/(g))(x) (fg)(x)=square ((f)/(g))(x)=square State the domain of each. Domain of (fg)(x) square Domain of ((f)/(g))(x) square : all real numbers xvert xneq 0 xvert xneq -2,0,2 xvert xneq 0,2 Evaluate the following. (fg)(-1)=square ((f)/(g))(-1)=square
Roztwór
Elizabeth
maestro · Tutor durante 5 años
4.1
(334 Votos)
Respuesta
\((fg)(x) = (x^2 + 9x + 20) \cdot (x^3 - 4x) = x^5 + 5x^4 - 36x^2 - 80x\)\((f/g)(x) = (x^2 + 9x + 20) / (x^3 - 4x) = (x + 5) / (x - 2)\)The domain of \((fg)(x)\) is all real numbers.The domain of \((f/g)(x)\) is
.\((fg)(-1) = (-1)^5 + 5(-1)^4 - 36(-1)^2 - 80(-1) = -1 + 5 - 36 + 80 = 48\)\((f/g)(-1) = (-1 + 5) / (-1 - 2) = 4 / -3 = -4/3\)
Explicación
## Step 1The problem involves the operations of function multiplication and division. The functions given are \(f(x) = x^2 + 9x + 20\) and \(g(x) = x^3 - 4x\).## Step 2To find the product of the two functions, we multiply them together. This is represented as \((fg)(x) = f(x) \cdot g(x)\).## Step 3To find the quotient of the two functions, we divide \(f(x)\) by \(g(x)\). This is represented as \((f/g)(x) = f(x) / g(x)\).## Step 4The domain of a function is the set of all possible input values (x-values) for which the function is defined. For the product and quotient of two functions, the domain is the intersection of the domains of the individual functions.## Step 5The domain of the product \((fg)(x)\) is all real numbers, because both \(f(x)\) and \(g(x)\) are defined for all real numbers.## Step 6The domain of the quotient \((f/g)(x)\) is all real numbers except for those that make the denominator zero. In this case, \(g(x) = x^3 - 4x = 0\) when
,
, or
. Therefore, the domain of \((f/g)(x)\) is all real numbers except
,
, and
.## Step 7To evaluate \((fg)(-1)\) and \((f/g)(-1)\), we substitute
into the expressions for \((fg)(x)\) and \((f/g)(x)\).