Mathematics, 13.04.2022 22:10 coltbergstrom

The graph of f(x) = -x2 - 2x + 8 is shown. Which of the following describes all solutions for f(x)? O(x -x2 - 2x + 8) for all real numbers
O(-4,0), (-1,9), (0, 8), (2.0)
O(-4.0), (2,0)
O(x, y) for all real numbers

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Answer from: heysonic91

f(x) = -x^2 - 2x + 8

y-intercept is when x = 0:

$\implies f(0) = -(0)^2 - 2(0) + 8=8$

So the y-intercept is (0, 8)

x-intercepts are when f(x) = 0:

$\implies f(x)=0$

$\implies -x^2 - 2x + 8=0$

$\implies x^2 + 2x - 8=0$

$\implies x^2 - 2x + 4x - 8=0$

$\implies x(x - 2) + 4(x-2)=0$

$\implies (x+4)(x - 2)=0$

Therefore:

$\implies (x+4)=0 \implies x=-4$

$\implies (x-2)=0 \implies x=2$

So the x-intercepts are (-4, 0) and (2, 0)

The vertex is the turning point of the parabola. The x-value of the vertex is the x-value between the 2 zeros (x-intercepts).

Therefore, the x-value of the vertex is $\sf \dfrac{x_1+x_2}{2}=\dfrac{-4+2}{2}=-1$

Substituting x = -1 into the function:

$\implies f(-1) = -(-1)^2 - 2(-1) + 8=9$

So the vertex is (-1, 9)

The domain is the input values, so x = all real numbers.

The range is the output values, so the range is $f(x)\leq 9$

Therefore, (-4, 0), (-1, 9), (0, 8) and (2, 0) are solutions of the function, HOWEVER they are not ALL the solutions.

All solutions of the function are:

(x, -x^2 - 2x + 8) for all real numbers of x

Answer from: Quest

none of the above.

for one of the equations to be used in the process, there has to be a $2x^2$ term in the equation since $2x$ squared is $2x^2$ .

since there is only a $x^2$ term in the first equation, we cannot derive a $2x+4$ from completing the square.

solving with completing the square

$x^2=-4x+3$

$x^2+4x=3$

$x^2+4x+4=7$

$(x+2)^2=7$

$x+2=+-\sqrt{7}$

$x=2+-\sqrt{7}$

Answer from: Quest

(2 x^3 + 7 x^2 + 5 x + 2)/(x (x + 2))

step-by-step explanation:

simplify the following:

x/x^2 + 3 x + 2 - (x (x + 1))/(x + 2)

combine powers. x/x^2 = x^(1 - 2):

x^(1 - 2) + 3 x + 2 - (x (x + 1))/(x + 2)

1 - 2 = -1:

x^(-1) + 3 x + 2 - (x (x + 1))/(x + 2)

put each term in 1/x + 3 x + 2 - (x (x + 1))/(x + 2) over the common denominator x (x + 2): 1/x + 3 x + 2 - (x (x + 1))/(x + 2) = (x + 2)/(x (x + 2)) + (3 x^2 (x + 2))/(x (x + 2)) + (2 x (x + 2))/(x (x + 2)) - (x^2 (x + 1))/(x (x + 2)):

(x + 2)/(x (x + 2)) + (3 x^2 (x + 2))/(x (x + 2)) + (2 x (x + 2))/(x (x + 2)) - (x^2 (x + 1))/(x (x + 2))

(x + 2)/(x (x + 2)) + (3 x^2 (x + 2))/(x (x + 2)) + (2 x (x + 2))/(x (x + 2)) - (x^2 (x + 1))/(x (x + 2)) = ((x + 2) + 3 x^2 (x + 2) + 2 x (x + 2) - x^2 (x + 1))/(x (x + 2)):

(2 + x + 3 x^2 (x + 2) + 2 x (x + 2) - x^2 (x + 1))/(x (x + 2))

3 x^2 (x + 2) = 3 x^3 + 6 x^2:

(2 + x + 3 x^3 + 6 x^2 + 2 x (x + 2) - x^2 (x + 1))/(x (x + 2))

2 x (x + 2) = 2 x^2 + 4 x:

(2 + x + 6 x^2 + 3 x^3 + 2 x^2 + 4 x - x^2 (x + 1))/(x (x + 2))

-x^2 (x + 1) = -x^2 - x^3:

(-x^2 - x^3 + 3 x^3 + 6 x^2 + 2 x^2 + 4 x + x + 2)/(x (x + 2))

grouping like terms, 3 x^3 - x^3 + 6 x^2 + 2 x^2 - x^2 + 4 x + x + 2 = (3 x^3 - x^3) + (6 x^2 + 2 x^2 - x^2) + (x + 4 x) + 2:

((3 x^3 - x^3) + (6 x^2 + 2 x^2 - x^2) + (x + 4 x) + 2)/(x (x + 2))

3 x^3 - x^3 = 2 x^3:

(2 x^3 + (6 x^2 + 2 x^2 - x^2) + (x + 4 x) + 2)/(x (x + 2))

6 x^2 + 2 x^2 - x^2 = 7 x^2:

(2 x^3 + 7 x^2 + (x + 4 x) + 2)/(x (x + 2))

x + 4 x = 5 x:

answer: (2 x^3 + 7 x^2 + 5 x + 2)/(x (x + 2))

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