Sovi.AI - AI Math Tutor

Scan to solve math questions

QUESTION IMAGE

6. keith determines the zeros of the function f(x) to be -6 and 5. what…

Question

  1. keith determines the zeros of the function f(x) to be -6 and 5. what could be keiths function?

a. $f(x) = (x + 5)(x + 6)$
b. $f(x) = (x + 5)(x - 6)$
c. $f(x) = (x - 5)(x + 6)$
d. $f(x) = (x - 5)(x - 6)$

  1. the zeros of the function $f(x) = 2x^3 + 12x - 11x^2$ are

a. ${2, 3}$
b. ${-1, 6}$
c. ${0, 2, 3}$
d. ${0, -1, 6}$

  1. which polynomial function has the zeros at -3, 0 and 4?

a. $f(x) = (x + 3)(x^2 + 4)$
b. $f(x) = (x^2 - 3)(x - 4)$
c. $f(x) = x(x + 3)(x - 4)$
d. $f(x) = x(x - 3)(x + 4)$

  1. explain how to determine the zeros of $f(x) = (x + 3)(x - 1)(x - 8)$. state the zeros of the function.
  1. the graph of the function $f(x) = ax^2 + bx + c$ is given. could the factors of $f(x)$ be $(x + 2)$ and $(x - 3)$? based on the graph, explain why or why not.

(there is a graph of a parabola here, but the text description is as above)

Explanation:

Question 6

Step1: Recall zero - factor property

If a function \(y = f(x)\) has a zero at \(x = a\), then \((x - a)\) is a factor of \(f(x)\). Given the zeros of the function \(f(x)\) are \(- 6\) and \(5\).
For the zero \(x=-6\), the corresponding factor is \((x-(-6))=(x + 6)\) (since if \(x=-6\), then \(x + 6=-6 + 6=0\)).
For the zero \(x = 5\), the corresponding factor is \((x - 5)\) (since if \(x = 5\), then \(x-5=5 - 5=0\)).

Step2: Form the function

So the function \(f(x)\) can be written as \(f(x)=(x - 5)(x + 6)\) (by multiplying the factors corresponding to each zero).
Now let's check the options:

  • Option a: \(f(x)=(x + 5)(x + 6)\), the zeros would be \(x=-5\) and \(x=-6\), not correct.
  • Option b: \(f(x)=(x + 5)(x - 6)\), the zeros would be \(x=-5\) and \(x = 6\), not correct.
  • Option c: \(f(x)=(x - 5)(x + 6)\), the zeros are \(x = 5\) (when \(x-5 = 0\)) and \(x=-6\) (when \(x + 6=0\)), correct.
  • Option d: \(f(x)=(x - 5)(x - 6)\), the zeros would be \(x = 5\) and \(x=6\), not correct.

Step1: Rewrite the function

First, rewrite the function \(f(x)=2x^{3}+12x - 11x^{2}\) in standard form (descending powers of \(x\)): \(f(x)=2x^{3}-11x^{2}+12x\).

Step2: Factor out the greatest common factor

Factor out the greatest common factor \(x\) from each term: \(f(x)=x(2x^{2}-11x + 12)\).

Step3: Factor the quadratic

Factor the quadratic \(2x^{2}-11x + 12\). We need two numbers \(a\) and \(b\) such that \(a\times b=2\times12 = 24\) and \(a + b=-11\). The numbers are \(-8\) and \(-3\).
So \(2x^{2}-11x + 12=2x^{2}-8x-3x + 12=2x(x - 4)-3(x - 4)=(2x - 3)(x - 4)\).

Step4: Find the zeros

Now, \(f(x)=x(2x - 3)(x - 4)\).
Set \(f(x)=0\):

  • \(x = 0\) (from the factor \(x\))
  • \(2x-3=0\Rightarrow x=\frac{3}{2}=1.5\) (wait, there is a mistake in the options? Wait, maybe I made a mistake in factoring. Let's try again.

Wait, \(2x^{2}-11x + 12\). Let's use the quadratic formula \(x=\frac{-b\pm\sqrt{b^{2}-4ac}}{2a}\) for \(ax^{2}+bx + c\). Here \(a = 2\), \(b=-11\), \(c = 12\).
\(\Delta=b^{2}-4ac=(-11)^{2}-4\times2\times12=121 - 96 = 25\)
\(x=\frac{11\pm\sqrt{25}}{4}=\frac{11\pm5}{4}\)
\(x_1=\frac{11 + 5}{4}=\frac{16}{4}=4\), \(x_2=\frac{11-5}{4}=\frac{6}{4}=\frac{3}{2}=1.5\)
Wait, the function is \(f(x)=x(2x - 3)(x - 4)\)? No, \(2x^{2}-11x + 12=(2x - 3)(x - 4)\) gives \(2x^{2}-8x-3x + 12=2x^{2}-11x + 12\), correct. Then the zeros are \(x = 0\), \(x=\frac{3}{2}\), \(x = 4\). But the options are a. \(\{2,3\}\), b. \(\{-1,6\}\), c. \(\{0,2,3\}\) (wait, maybe the original function was \(f(x)=2x^{3}-11x^{2}+12x\) is mis - written? Wait, maybe the function is \(f(x)=2x^{3}-11x^{2}+12x\) is actually \(f(x)=2x^{3}-11x^{2}+12x\), but maybe there is a typo and the function is \(f(x)=2x^{3}-11x^{2}+12x\) or maybe \(f(x)=2x^{3}-7x^{2}-12x\)? Let's check with \(f(x)=2x^{3}-7x^{2}-12x\). Then \(f(x)=x(2x^{2}-7x - 12)=x(2x^{2}-8x + x - 12)=x[2x(x - 4)+1(x - 4)]=x(2x + 1)(x - 4)\), no. Wait, maybe the function is \(f(x)=2x^{3}-11x^{2}+12x\) and the options have a mistake, but looking at the options, option c is \(\{0,2,3\}\), maybe the function is \(f(x)=2x^{3}-11x^{2}+12x\) is actually \(f(x)=2x^{3}-11x^{2}+12x\) with a factoring error. Wait, maybe the original function is \(f(x)=2x^{3}-7x^{2}-12x\)? No, let's go back. The problem says "The zeros of the function \(f(x)=2x^{3}+12x - 11x^{2}\) are". Let's re - arrange: \(f(x)=2x^{3}-11x^{2}+12x=x(2x^{2}-11x + 12)\). Let's use the quadratic formula for \(2x^{2}-11x + 12\): \(x=\frac{11\pm\sqrt{121 - 96}}{4}=\frac{11\pm5}{4}\), so \(x = 4\) or \(x=\frac{3}{2}\). So the zeros are \(x = 0\), \(x=\frac{3}{2}\), \(x = 4\). But the options don't match. Maybe there is a mistake in the problem. But assuming that the function is \(f(x)=2x^{3}-11x^{2}+12x\) and there is a typo, and the intended function is \(f(x)=2x^{3}-7x^{2}-12x\), then \(f(x)=x(2x^{2}-7x - 12)=x(2x + 3)(x - 4)\), no. Alternatively, if the function is \(f(x)=2x^{3}-11x^{2}+12x\), and the options are wrong, but among the given options, option c is \(\{0,2,3\}\), maybe the function is \(f(x)=2x^{3}-11x^{2}+12x\) is actually \(f(x)=2x^{3}-7x^{2}-12x\) is not. Wait, maybe I made a mistake in the sign. The function is \(f(x)=2x^{3}+12x-11x^{2}=2x^{3}-11x^{2}+12x\). Let's plug \(x = 0\): \(f(0)=0\), \(x = 2\): \(f(2)=2\times8-11\times4 + 12\times2=16-44 + 24=-4
eq0\), \(x = 3\): \(f(3)=2\times27-11\times9+12\times3=54 - 99+36=-9
eq0\). \(x=-1\): \(f(-1)=2\times(-1)-11\times1+12\times(-1)=-2-11 - 12=-25
eq0\), \(x = 6\): \(f(6)=2\times216-11\times36+12\times6=432-396 + 72=108
eq0\). There must be a typo in the problem. But if we assume that th…

Step1: Recall zero - factor property

If a polynomial function has a zero at \(x = a\), then \((x - a)\) is a factor of the polynomial. Given the zeros of the polynomial function are \(-3\), \(0\) and \(4\).

  • For the zero \(x=-3\), the corresponding factor is \((x-(-3))=(x + 3)\).
  • For the zero \(x = 0\), the corresponding factor is \(x\) (since if \(x = 0\), then \(x=0\)).
  • For the zero \(x = 4\), the corresponding factor is \((x - 4)\).

Step2: Form the polynomial function

So the polynomial function \(f(x)\) is the product of these factors: \(f(x)=x(x + 3)(x - 4)\).
Now let's check the options:

  • Option a: \(f(x)=(x + 3)(x^{2}+4)\), the zeros of \(x^{2}+4 = 0\) are imaginary (\(x=\pm2i\)), so the real zeros are only \(x=-3\), not correct.
  • Option b: \(f(x)=(x^{2}-3)(x - 4)\), the zeros of \(x^{2}-3=0\) are \(x=\pm\sqrt{3}\) and \(x = 4\), not correct.
  • Option c: \(f(x)=x(x + 3)(x - 4)\), the zeros are \(x = 0\) (from \(x\)), \(x=-3\) (from \(x + 3\)) and \(x = 4\) (from \(x - 4\)), correct.
  • Option d: \(f(x)=x(x - 3)(x + 4)\), the zeros are \(x = 0\), \(x = 3\) and \(x=-4\), not correct.

Answer:

c. \(f(x)=(x - 5)(x + 6)\)

Question 7