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## anonymous 5 years ago Solve. 2x2 + 20x = –38 a. –5 ± √14 b. –5 ± √51 c. –5 ± √6 d. –5 ± √13

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1. anonymous

c as usual. why is it always c?

2. anonymous

can u show me how, though, im trying hard to remember but its not coming to me...

3. anonymous

ok first off each term has a factor of 2, so we can make our life easier by writing $x^2+10x=-19$

4. anonymous

then we can write the left hand side as a perfect square , by taking half of 10, which is 5, squaring and adding it to both sides to get $(x+5)^2=-19+25=6$

5. anonymous

then take the square root, don't forget the plus and minus $x+5=\pm\sqrt{6}$ then subtract 5 $x=-5\pm\sqrt{6}$

6. anonymous

oh i get it now, and this is for all problems like this?

7. anonymous

yes you can always use this method. if you like you could write $x^2+10x+19=0$ and then use the quadratic formula, but that would be more work because you would have a denominator, and then you would have to simplify the radical, factor and cancel to get the answer you see above

8. anonymous

oh okay, thanks. can u also help me with http://openstudy.com/study?F295750376716BE3I5S=_#/updates/4f178119e4b0aeb795f57dc2

9. anonymous

if the coefficient of the "middle term" is even, then it is much easier to complete the square

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