document.write( "Question 484807: I need help with inequalities problems, I don't know a thing!!! \n" ); document.write( "
Algebra.Com's Answer #331640 by MathLover1(20849)\"\" \"About 
You can put this solution on YOUR website!
THIS SIGN < means is less than.. \r
\n" ); document.write( "\n" ); document.write( "This sign > means is greater than. \r
\n" ); document.write( "\n" ); document.write( "In each case, the sign opens towards the larger number.\r
\n" ); document.write( "\n" ); document.write( "For example, \"2+%3C5\" (\"2 is less than 5\"). Equivalently, \"+5+%3E+2\"} (\"5 is greater than 2\").\r
\n" ); document.write( "\n" ); document.write( "These are the two senses of an \"inequality\": < and > , \r
\n" ); document.write( "\n" ); document.write( "and you also might have ≤, \"is less than or equal to\" or ≥, \"is greater than or equal to\"\r
\n" ); document.write( "\n" ); document.write( "On the number line, \"a+%3C+b\" means: a falls to the left of \"b\".\r
\n" ); document.write( "\n" ); document.write( "ex.:
\n" ); document.write( "\"2%3C+5\"
\n" ); document.write( "
\n" ); document.write( "−1 < 2\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "a compound inequality:\r
\n" ); document.write( "\n" ); document.write( "\"x+%3E+1\" and x ≤ 5.\r
\n" ); document.write( "\n" ); document.write( "It is a compound sentence whose conjunction is \"and.\" It says that x takes on values that are greater than 1 and less than or equal to 5. \r
\n" ); document.write( "\n" ); document.write( "It is within that interval that x takes its values. The endpoint 1 is not included. x is definitely greater than 1; we indicate that by placing a parenthesis \"(\". The endpoint 5 is included; we indicate that by placing a bracket \"]\".\r
\n" ); document.write( "\n" ); document.write( "A continued inequality\r
\n" ); document.write( "\n" ); document.write( "\"a+%3C+x+%3C+b\"\r
\n" ); document.write( "\n" ); document.write( "That is called a continued inequality. It means\r
\n" ); document.write( "\n" ); document.write( "\"a+%3C+x\" and \"x+%3C+b\"\r
\n" ); document.write( "\n" ); document.write( "A continued inequality always implies the conjunction and. The sense is always < or ≤.\r
\n" ); document.write( "\n" ); document.write( "The continued inequality means:\r
\n" ); document.write( "\n" ); document.write( "x falls in the interval between a and b.\r
\n" ); document.write( "\n" ); document.write( "\"\"a+%3C+x+%3C+b\"\" illustrates that\r
\n" ); document.write( "\n" ); document.write( "Some theorems of inequalities\r
\n" ); document.write( "\n" ); document.write( "To prove a statement whose predicate is \"is greater than,\" we must have a definition of \"is greater than.\" We shall adopt the following. We shall define \"a is greater than b\" to mean: a − b is positive. \r
\n" ); document.write( "\n" ); document.write( "Algebraically:\r
\n" ); document.write( "\n" ); document.write( "\"a+%3E+b\" if and only if a − b > 0\r
\n" ); document.write( "\n" ); document.write( "Theorem 1. We may add the same number to both sides of an inequality, and the sense will not change.\r
\n" ); document.write( "\n" ); document.write( "Theorem 1 as follows:\r
\n" ); document.write( "\n" ); document.write( "\"a+%3E+b\"
\n" ); document.write( " means
\n" ); document.write( "
\n" ); document.write( "a − b > 0\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "upon adding and subtracting c :
\n" ); document.write( "
\n" ); document.write( "a − b + c − c > 0
\n" ); document.write( "
\n" ); document.write( "(a + c) − (b + c) > 0\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "Theorem 2. We may multiply both sides of an inequality by the same positive number, and the sense will not change.\r
\n" ); document.write( "\n" ); document.write( "If
\n" ); document.write( " a > b, and c > 0,
\n" ); document.write( "
\n" ); document.write( "then
\n" ); document.write( "
\n" ); document.write( " ca>cb.\r
\n" ); document.write( "\n" ); document.write( "For example:\r
\n" ); document.write( "\n" ); document.write( " 4 > −5\r
\n" ); document.write( "\n" ); document.write( "If we now multiply both sides by 3, for example, then
\n" ); document.write( "
\n" ); document.write( " 12 > −15.\r
\n" ); document.write( "\n" ); document.write( "The sense does not change.\r
\n" ); document.write( "
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "
\n" ); document.write( "
\n" );