Your Algebra Homework Can Now Be Easier Than Ever!

Math 91 Exam 1 Solutions

1. (4 pts each) Do the following computations with complex numbers . You don’t need to explain
why you do the computations the way you do, but be sure to show the details of your work.

2. (5 pts each) Find the following greatest common divisors . You don’t need to explain why
you do the computations the way you do, but be sure to show the details of your work.

(c) gcd since the two numbers have no prime factors in common.

3. (5 pts each) Let z = x + yi be any complex number.
(a) Find |z|.

(b) Find .

(c) Compare the results of (a) and (b). Explain why this happens.

They are the same. The absolute value of a
complex
number is its distance from 0 in the
complex plane. A number and its conjugate
are mirror images of each other across the real
axis. So their distances from 0 must be the
same.

4. (a) (4 pts) Explain what it means that multiplication on the integers is associative. Give
an example of this. (You are not asked to prove that multiplication is associative, only
to explain what the term means .)

It means that (xy)z = x(yz) for any three integers x, y, z. For example,

(2 · 3) · 4 = 6 · 4 = 24
2 · (3 · 4) = 2 · 12 = 24.

(b) (4 pts) Explain what it means that multiplication on the rational numbers is associative.
Give an example of this. (You are not asked to prove that multiplication is associative,
only to explain what the term means.)

It means that (xy)z = x(yz) for any three rational numbers x, y, z. For example,

(c) (6 pts) Assume that multiplication is associative on the integers. Use this to justify that
multiplication is also associative on the rational numbers. (You are now asked to prove
that multiplication is associative on the rationals.)

Let x, y, z ∈ Q. Then there exist integers m, n, p, q, r, s such that n, q, s ≠ 0 and x =
m/n, y = p/q, and z = r/s.

Since multiplication is associative on the integers (mp)r = m(pr) and (nq)s = n(qs).
Therefore

5. Extra credit problem. The quadratic equation x ^2 −3x+5 = 0 has no real solutions. But
it has two complex solutions. You can find them using the usual quadratic formula .
(a) (4 pts) Find the two solutions of x ^2 − 3x + 5 = 0.

The solutions are

(b) (4 pts) Let A and B denote the two solutions you found in part (a). Verify (by doing
the actual computation) that (x − A)(x − B) = x^2 − 3x + 5.

(c) (7 pts) Compute A+B and AB. What do these have to do with the original equation ?
Explain why this happens.

Actually, notice we already computed A + B and AB in part (b):

Notice that −(A + B) = −3 is the coefficient of x and AB = 5 is the constant term in
the original equation. This must be so since

Incidentally, the same is true when the roots are real and that is standard material in
Algebra I together with the quadratic formula .

Prev Next

Start solving your Algebra Problems in next 5 minutes!

Algebra Helper
Download (and optional CD)

Only $39.99

Click to Buy Now:


OR

2Checkout.com is an authorized reseller
of goods provided by Sofmath

Attention: We are currently running a special promotional offer for Algebra-Answer.com visitors -- if you order Algebra Helper by midnight of November 2nd you will pay only $39.99 instead of our regular price of $74.99 -- this is $35 in savings ! In order to take advantage of this offer, you need to order by clicking on one of the buttons on the left, not through our regular order page.

If you order now you will also receive 30 minute live session from tutor.com for a 1$!

You Will Learn Algebra Better - Guaranteed!

Just take a look how incredibly simple Algebra Helper is:

Step 1 : Enter your homework problem in an easy WYSIWYG (What you see is what you get) algebra editor:

Step 2 : Let Algebra Helper solve it:

Step 3 : Ask for an explanation for the steps you don't understand:



Algebra Helper can solve problems in all the following areas:

  • simplification of algebraic expressions (operations with polynomials (simplifying, degree, synthetic division...), exponential expressions, fractions and roots (radicals), absolute values)
  • factoring and expanding expressions
  • finding LCM and GCF
  • (simplifying, rationalizing complex denominators...)
  • solving linear, quadratic and many other equations and inequalities (including basic logarithmic and exponential equations)
  • solving a system of two and three linear equations (including Cramer's rule)
  • graphing curves (lines, parabolas, hyperbolas, circles, ellipses, equation and inequality solutions)
  • graphing general functions
  • operations with functions (composition, inverse, range, domain...)
  • simplifying logarithms
  • basic geometry and trigonometry (similarity, calculating trig functions, right triangle...)
  • arithmetic and other pre-algebra topics (ratios, proportions, measurements...)

ORDER NOW!

Algebra Helper
Download (and optional CD)

Only $39.99

Click to Buy Now:


OR

2Checkout.com is an authorized reseller
of goods provided by Sofmath
Check out our demo!
 
"It really helped me with my homework.  I was stuck on some problems and your software walked me step by step through the process..."
C. Sievert, KY
 
 
Sofmath
19179 Blanco #105-234
San Antonio, TX 78258
Phone: (512) 788-5675
Fax: (512) 519-1805
 

Home   : :   Features   : :   Demo   : :   FAQ   : :   Order

Copyright © 2004-2024, Algebra-Answer.Com.  All rights reserved.