find 2 + 2 + 2 + 2 + . . .
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Move the 2 over to form 2 + 2 + 2 + . . . = − 2 and square both sides ( 2 + 2 + 2 + . . . ) 2 = ( − 2 ) 2 . What you will get is 2 + 2 + 2 + 2 + . . . = 4 , which is what we want. Thus our answer is 4 Ans.
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Let 2 + 2 + 2 + 2 + . . . = x
Next, subtract 2 from both sides and square both sides, the equation becomes:
2 + 2 + 2 + 2 + . . . = ( x − 2 ) 2 .
Notice how the left side becomes x again, and by substituting on the left side and distributing on the right side, we get the following equation:
x = x 2 − 4 x + 4
x 2 − 5 x + 4 = 0
( x − 4 ) ( x − 1 ) = 0 so x = 1 , 4 .
Obviously, the answer must be greater than 2 because the first term is 2 and we're adding positive values. Knowing that x must be greater than 2 , we can eliminate 1 from the solution set and that leaves us with the final answer: 4 .