Saturday

December 20, 2014

December 20, 2014

Posted by **Trudy** on Saturday, January 20, 2007 at 11:14pm.

Alright so in an arithmetic squence the difference d between any two successive numbers is constant. So if the first term is x, then the second term is (x+d), and the third term is (x+2d), etc. up to the tenth term in this case which is (x+9d). We know that the eighth term is 5 so this gives...

x+7d=5

and we know that the sum of the first ten terms is 20 which gives...

x+(x+d)+(x+2d)+(x+3d)+...+(x+9d)=20

or..

10x+45d=20

Solve these two equations for x and d..

x+7d=5

10x+45d=20

I get... d=1.2 and x=-3.4

Hope that helps

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