document.write( "Question 121334This question is from textbook Demana, Waits, Foley, Kennedy Precalculus Graphical, Numerical, Algebraic
\n" ); document.write( ": Can you please help me understand the method of arriving at the answer of this problem? Thank you.\r
\n" ); document.write( "\n" ); document.write( "In my textbook this was the exercise question
\n" ); document.write( " Write the product in standard form:
\n" ); document.write( "(2+3i)(2-i) \r
\n" ); document.write( "\n" ); document.write( "The answer in the back of the book was X= -4 +or- the sqrt of the fraction 8/3.\r
\n" ); document.write( "\n" ); document.write( "I don't understand how they arrived at this answer. \n" ); document.write( "

Algebra.Com's Answer #89050 by Edwin McCravy(20054) $\"\"$ $\"About$

You can put this solution on YOUR website!
Can you please help me understand the method of arriving at the answer of this problem? Thank you.
\n" ); document.write( "In my textbook this was the exercise question
\n" ); document.write( "Write the product in standard form:
\n" ); document.write( "(2+3i)(2-i)
\n" ); document.write( "

\r\n" );
document.write( "\r\n" );
document.write( "   F        O          I         L       \r\n" );
document.write( "(2)(2) + (2)(-i) + (3i)(2) + (3i)(-i)\r\n" );
document.write( "\r\n" );
document.write( "   4   -   2i    +    6i   -   3i²\r\n" );
document.write( "\r\n" );
document.write( "             4 + 4i - 3(-1)\r\n" );
document.write( "           \r\n" );
document.write( "              4 + 4i + 3\r\n" );
document.write( "\r\n" );
document.write( "                7 + 4i\r\n" );
document.write( "\r\n" );
document.write( "\r\n" );
document.write( "\r\n" );
document.write( "The answer in the back of the book was \r\n" );
document.write( "X= -4 +or- the sqrt of the fraction 8/3. \r\n" );
document.write( "\r\n" );
document.write( "I don't understand how they arrived at this answer.\r\n" );
document.write( "\r\n" );
document.write( "I don't either. I think you looked at the answer\r\n" );
document.write( "to this problem instead:\r\n" );
document.write( "\r\n" );
document.write( "Solve for x by completing the square:\r\n" );
document.write( "\r\n" );
document.write( "       3x² + 24x + 40 = 0\r\n" );
document.write( "\r\n" );
document.write( "            3x² + 24x = -40\r\n" );
document.write( "\r\n" );
document.write( "              x² + 8x = \r\n" );
document.write( "\r\n" );
document.write( "8·1/2 = 4, 4² = 16, so add + 16 to both sides\r\n" );
document.write( "\r\n" );
document.write( "         x² + 8x + 16 =  + 16\r\n" );
document.write( "\r\n" );
document.write( "       (x + 4)(x + 4) =  + \r\n" );
document.write( "\r\n" );
document.write( "             (x + 4)² = \r\n" );
document.write( "\r\n" );
document.write( "Use square root principle:\r\n" );
document.write( "                         \r\n" );
document.write( "                x + 4 = ±\r\n" );
document.write( "\r\n" );
document.write( "                    x = -4 ± \r\n" );
document.write( "\r\n" );
document.write( "Edwin

\n" ); document.write( "

\n" );