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2 years ago

Given the function f(x)=3^x, find the value of f^-1(27)

Mathematics

1 answer:

Shalnov [3]2 years ago

7 0

This is asking you to solve the equation ...

... 27 = 3^x

You can use logarithms to find

... log(27) = x·log(3)

... log(27)/log(3) = x = 1.43136376.../0.47712125...

... x = 3

Or, you can use your knowledge of small cubes and match exponents.

... 3^3 = 3^x

... 3 = x

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Find the polynomial of minimum degree, with real coefficients, zeros at

drek231 [11]

Answer:

$\huge\boxed{p(x)=4x^3-20x^2+4x+300}$

Step-by-step explanation:

$\text{If}\ x=4\pm3i\ \text{and}\ x=-3\ \text{are the zeros of a polynomial, then it has a form:}\\\\p(x)=\bigg(x-(4-3i)\bigg)\bigg(x-(4+3i)\bigg)\bigg(x-(-3)\bigg)\bigg(r(x)\bigg)\\\\p(x)=(x-4+3i)(x-4-3i)(x+3)\bigg(r(x)\bigg)\\\\p(x)=\underbrace{\bigg((x-4)+3i\bigg)\bigg((x-4)-3i\bigg)}_{\text{use}\ (a+b)(a-b)=a^2-b^2}(x+3)\bigg(r(x)\bigg)\\\\p(x)=\bigg((x-4)^2-(3i)^2\bigg)(x+3)\bigg(r(x)\bigg)\qquad\text{use}\ (a-b)^2=a^2-2ab+b^2$

$p(x)=(x^2-2(x)(4)+4^2-3^2i^2)(x+3)\bigg(r(x)\bigg)\qquad\text{use}\ i^2=-1\\\\p(x)=(x^2-8x+16-9(-1))(x+3)\bigg(r(x)\bigg)\\\\p(x)=(x^2-8x+16+9)(x+3)\bigg(r(x)\bigg)\\\\p(x)=(x^2-8x+25)(x+3)\bigg(r(x)\bigg)\qquad\text{use FOIL}:\ (a+b)(c+d)=ac+ad+bc+bd\\\\p(x)=\bigg((x^2)(x)+(x^2)(3)+(-8x)(x)+(-8x)(3)+(25)(x)+(25)(3)\bigg)\bigg(r(x)\bigg)\\\\p(x)=(x^3+3x^2-8x^2-24x+25x+75)\bigg(r(x)\bigg)\qquad\text{combine like terms}\\\\p(x)=(x^3-5x^2+x+75)\bigg(r(x)\bigg)$

$\text{The y-intercept is at 300}.\\\\\text{For}\ w(x)=a_nx^n+a_{n-1}x^{n-1}+a_{n-2}x^{n-2}+...+a_1x+a_0\\\\\text{y-intercept is}\ a_0\\\\\text{Therefore for}\ p(x)=(x^3-5x^2+x+75)\bigg(r(x)\bigg)\\\\\text{y-intercet is}\ 75\bigg(r(x)\bigg)\\\\75\bigg(r(x)\bigg)=300\qquad\text{divide both sides by 75}\\\\r(x)=4\\\\\text{Finally:}\\\\p(x)=(x^3-5x^2+x+75)(4)\qquad\text{use the distributive property}\\\\p(x)=(x^3)(4)+(-5x^2)(4)+(x)(4)+(75)(4)\\\\p(x)=4x^3-20x^2+4x+300$

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3 years ago

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Kipish [7]

The answer would be 15

6 0

3 years ago

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Which does not show a direct variation between x and y?

Dmitry [639]

$(1)\\direct\ variation\ between\ x\ and\ y:\ \ \ y=k\cdot x\ \ \ and\ \ \ k\in\ R\\\\Ans.\ NOT\ direct\ is\ D\\\\(2)\\f(x) = m\cdot x\ \ \ and\ \ \ f(6)=8\\\\ \Rightarrow\ \ \ m\cdot 6=8\ \ \ \Rightarrow\ \ \ m= \frac{8}{6} = \frac{4}{3} \ \ \ \ \Rightarrow\ \ \ \ Ans.\ D\\\\(3)\\f(x)=30x\ \ \ \Leftrightarrow\ \ \ \frac{f(x)}{x} =30\ \ \ \ \ \ \Rightarrow\ \ \ \ constans=30\ \ \ \ Ans.\ B.$

$\\\\(4)\\f(x)=m\cdot x\ \ and\ \ f(8)=56\\\\m\cdot8=56\ \ \Leftrightarrow\ \ m= \frac{56}{8} =7\ \ \Rightarrow\ \ \ f(x)=7x\ \ \ \Rightarrow\ \ \ f(2)=7\cdot2=14\\\\Ans.\ D.$

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Step-by-step explanation:

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