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Question
Using the method of completion of squares find one of the roots of the equation 2x27x+3=0. Also, find the equation obtained after completion of the square.
Options:
A .  6, (x−74)2−2516=0
B .  3, (x−74)2−2516=0
C .  3, (x−72)2−2516=0
D .  13, (x−72)2−2516=0
Answer: Option B
:
B
2x27x+3=0
Dividing by the coefficient of x2, we get
x272x+32=0;a=1,b=72,c=32

Adding and subtracting the square of b2=74, (half of coefficient of x)
we get,
[x22(74)x+(74)2](74)2+32=0

The equation after completing the square is :
(x74)22516=0

Taking square root, (x74)=(±54)
Taking positive sign 54,x=3
Taking negative sign 54,x=12

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