Gareth56 Posted November 6, 2008 Share Posted November 6, 2008 When I read " We work out this example as if it were 3(x - y) - 5(2y - x). We begin by multiplying out using the distributive property" Does "multiplying out using the distributive property" just mean multiplying everything inside the bracket by what's outside it, in this case 3 & 5? Link to comment Share on other sites More sharing options...
DrP Posted November 6, 2008 Share Posted November 6, 2008 Pretty much yes. It means the x AND the -y both get multiplyed by the 3 (the factor 3 is distributed through each term in the brackets) and the 2y and the - x get multiplied by the 5 (the factor 5 is distributed through that set of brackets). Therefore it expands to: 3x - 3y -10y + 5x (care with the PLUS 5x.... - x -) Link to comment Share on other sites More sharing options...
Kyrisch Posted November 6, 2008 Share Posted November 6, 2008 To further clarify, the problem is more like 3 (x + -y) + -5 (2y + -x). You must distribute the -5 therefore making the last term -(-5x) = +5x. Link to comment Share on other sites More sharing options...
the tree Posted November 6, 2008 Share Posted November 6, 2008 Knowing that the distributive property is there, so that 'multiplying out' is a valid operation is important: For the sake of rigour Because sometimes the distributive property doesn't hold. Link to comment Share on other sites More sharing options...
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