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Q.

Solve x2+8x+15=0 by method of completing square.

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a

x=3,5

b

x=3,-5

c

x=-3,5  

d

x=-3,-5

answer is A.

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Detailed Solution

It is given that x2+8x+15=0.
We use the method of completing square, x2+8x=-15.
By adding 16 on both sides, we get a perfect square on the left side and balance the equation as well.
  ⇒ x 2 +8x+16=−15+16 ⇒ (x+4) 2 =1 ⇒x+4=±1 ⇒x=−4+1,x=−4−1  
⇒x=-3,x=-5
Hence, the values of x is -3, -5.
Hence, the correct option is 1.
 
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