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3 years ago

Manuel noticed that his cellphone bill reflected a monthly fee of

Mathematics

1 answer:

Aneli [31]3 years ago

8 0

Answer:

He spent on 16 minutes

Step-by-step explanation:

Given

$Base\ Amount = \$40$

$Charge = \$0.5$ per minute

$Total = \$48$

Required

Determine the number of minutes

Let the number of minutes be n

<em>If 1 minute costs $0.5</em>

<em>n minutes would cost $0.5n</em>

The relationship between the given parameters is

$Total = Base\ Amount + Charges$

Substitute values for each of the above

$48 = 40 + 0.5n$

Solve for 0.5n

$0.5n = 48 - 40$

$0.5n = 8$

Solve for n

$n = 8/0.5$

$n = 16$

<em>He spent on 16 minutes</em>

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Find a factorization of x² + 2x³ + 7x² - 6x + 44, given that<br> −2+i√√7 and 1 - i√/3 are roots.

Levart [38]

A factorization of $x^4+2x^3+7x^2-6x+44$ is $(x^2+4x+11)(x^2-2x+4)$ .

<h3>What are the properties of roots of a polynomial?</h3>

The maximum number of roots of a polynomial of degree $n$ is $n$ .
For a polynomial with real coefficients, the roots can be real or complex.
The complex roots of a polynomial with real coefficients always exist in a pair of conjugate numbers i.e., if $a+ib$ is a root, then $a-ib$ is also a root.

If the roots of the polynomial $p(x)=ax^4+bx^3+cx^2+dx+e$ are $r_1,r_2,r_3,r_4$ , then it can be factorized as $p(x)=(x-r_1)(x-r_2)(x-r_3)(x-r_4)$ .

Here, we are to find a factorization of $p(x)=x^4+2x^3+7x^2-6x+44$ . Also, given that $-2+i\sqrt{7}$ and $1-i\sqrt{3}$ are roots of the polynomial.

Since $p(x)=x^4+2x^3+7x^2-6x+44$ is a polynomial with real coefficients, so each complex root exists in a pair of conjugates.

Hence, $-2-i\sqrt{7}$ and $1+i\sqrt{3}$ are also roots of the given polynomial.

Thus, all the four roots of the polynomial $p(x)=x^4+2x^3+7x^2-6x+44$ , are: $r_1=-2+i\sqrt{7}, r_2=-2-i\sqrt{7}, r_3=1-i\sqrt{3}, r_4=1+i\sqrt{3}$ .

So, the polynomial $p(x)=x^4+2x^3+7x^2-6x+44$ can be factorized as follows:

$\{x-(-2+i\sqrt{7})\}\{x-(-2-i\sqrt{7})\}\{x-(1-i\sqrt{3})\}\{x-(1+i\sqrt{3})\}\\=(x+2-i\sqrt{7})(x+2+i\sqrt{7})(x-1+i\sqrt{3})(x-1-i\sqrt{3})\\=\{(x+2)^2+7\}\{(x-1)^2+3\}\hspace{1cm} [\because (a+b)(a-b)=a^2-b^2]\\=(x^2+4x+4+7)(x^2-2x+1+3)\\=(x^2+4x+11)(x^2-2x+4)$