if a number is added to twice its square ,the result is 21 . find the number.
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3 is the right number
Answered by
1
Answer:
The answer is : 3 , -7/2
Step-by-step explanation:
Let the number be x
According to the question ,
2x^2 + x = 21
2x^2 + x -21 = 0
2x^2 - 6x + 7x -21 = 0 (by splitting middle term)
2x(x-3) 7(x-3) = 0
(x-3)(2x+7) = 0
Case (i)
x-3 = 0
x = 3
Case (ii)
2x + 7 = 0
2x = -7
x = -7/2
Answer : x = 3 , -7/2
The number is 3 , -7/2
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