Solve each equation by completing the square. if necessary found to the neares hundred.
x^2-x=2
@ganeshie8
take half of "x" coefficient
add its square both sides
ok so 1^2
what is "x" coefficient ?
1
whats half of 1 ?
1/2
\(\large x^2-x=2\) \(\large x^2-2\times \frac{1}{2}x=2\)
so, add the missing \(\left(\frac{1}{2}\right)^2\) both sides, so that we can comlete the square
why is i t times
\(\large x^2-x=2 \) \(\large x^2-2\times \frac{1}{2}x=2\) \(\large x^2-2\times \frac{1}{2}x + \left(\frac{1}{2}\right)^2=2 + \left(\frac{1}{2}\right)^2\)
In the second step, I have just wrote 1 as 2*1/2
2*1/2 = 1, so... nothing fishy ok ?
Next, look at the left hand side once, does the pattern look familiar ?
\(\large a^2 - 2a b + b^2 \)
??
what
you should know this identity : \(\large a^2 -2ab + b^2 = (a-b)^2 \)
the left hand side is exactly of above form, so we can write it as a perfect square
\(\large x^2-x=2 \) \(\large x^2-2\times \frac{1}{2}x=2\) \(\large x^2-2\times \frac{1}{2}x + \left(\frac{1}{2}\right)^2=2 + \left(\frac{1}{2}\right)^2\) rewriting the left hand side using a known identity : \(a^2-2ab+b^2 = (a-b)^2\) \(\large \left( x - \frac{1}{2}\right)^2 =2 + \left(\frac{1}{2}\right)^2\) simplifying the right hand side : \(\large \left( x - \frac{1}{2}\right)^2 = \frac{9}{4}\)
take square root both sides
\(\large x^2-x=2 \) \(\large x^2-2\times \frac{1}{2}x=2\) \(\large x^2-2\times \frac{1}{2}x + \left(\frac{1}{2}\right)^2=2 + \left(\frac{1}{2}\right)^2\) rewriting the left hand side using a known identity : \(a^2-2ab+b^2 = (a-b)^2\) \(\large \left( x - \frac{1}{2}\right)^2 =2 + \left(\frac{1}{2}\right)^2\) simplifying the right hand side : \(\large \left( x - \frac{1}{2}\right)^2 = \frac{9}{4}\) take square root both sides : \(\large x - \frac{1}{2} = \pm \frac{3}{2}\)
you get : \(\large x = 2, -1\)
we're done. let me knw if somthng doesnt make sense
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