SOLUTION: This is actually for QUADRATIC FORMULA, NOT QUADRATIC EQUATION Solve by completing the square 2x^2 + 11x - 1 = 0 The solution set is { }

Algebra ->  Quadratic Equations and Parabolas  -> Quadratic Equations Lessons  -> Quadratic Equation Lesson -> SOLUTION: This is actually for QUADRATIC FORMULA, NOT QUADRATIC EQUATION Solve by completing the square 2x^2 + 11x - 1 = 0 The solution set is { }      Log On


   

Question 625211: This is actually for QUADRATIC FORMULA, NOT QUADRATIC EQUATION
Solve by completing the square
2x^2 + 11x - 1 = 0
The solution set is { }
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
+2x%5E2+%2B+11x+-+1+=+0+
First add +1+ to both sides
+2x%5E2+%2B+11x+=+1+
Now divide both sides by +2+
+x%5E2+%2B+%2811%2F2%29%2Ax+=+1%2F2+
------------
In order to complete the square, take
1/2 of the coefficient of the +x+ term,
square it, then add it to both sides
------------------
+x%5E2+%2B+%2811%2F2%29%2Ax+%2B+%2811%2F4%29%5E2+=+1%2F2+%2B+%2811%2F4%29%5E2+
+x%5E2+%2B+%2811%2F2%29%2Ax+%2B+121%2F16+=+8%2F16+%2B+121%2F16+
+%28+x+%2B+11%2F4+%29%5E2+=+129%2F16+
Take the square root of both sides
+x+%2B+11%2F4+=+sqrt%28129%29%2F4+
+x+=+%28+-11+%2B+sqrt%28129%29+%29+%2F+4+
and
+x+=+%28+-11+-+sqrt%28129%29+%29+%2F+4+
-------------------------
check:
+2x%5E2+%2B+11x+-+1+=+0+



+121%2F8+%2B+129%2F8+-242%2F8+-+8%2F8+=+0+
+250%2F8+-+250%2F8+=+0+
+0+=+0+
OK
You can check other root