Question 278740: This question deals with solving quadratic equations by completing the square. The question wants me to approximate the solution to the nearest thousanth. The question reads: t^2-4t=7, I believe the next step is to multiply each side by 1/2 but not sure if that is right or what to do after that. ANy help is much appreciated, Thanks
Answer by solver91311(24713)   (Show Source):
You can put this solution on YOUR website!
Close, but not quite.
You have:
You want to add a value to both sides so that the LHS is a perfect square trinomial. Here's where the  comes in. Divide the coefficient on the first degree term by 2. -4 divided by 2 is -2. Then square this value, -2 squared is 4. Now, add 4 to both sides:
Next, factor the RHS:
^2\ =\ 11)
Take the square root of both sides, remembering to consider both positive and negative roots in the LHS:
Finally add 2 to both sides:
Now you can use a calculator and round off, or, if you are really supposed to just make an estimate, proceed thus:
3 squared is 9, 4 squared is 16. 16 - 9 is 7 and 16 minus 11 is 5 2/7 is about .3, so root 11 is very close to 3.3. 2 plus 3.3 is 5.3 and 2 minus 3.3 is -1.3.
The calculator says: 5.3166, -1.3166
John
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