IF a number is added to twice its square then the resultant is 21
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Answer:
The answer is 3
Step-by-step explanation:
Let the no. be x
According to the question,
x + 2x^2 = 21
We can obtain a quadratic equation,
2x^2 + x - 21 =0
On solving the above equation,we get
2x^2 - 6x + 7x - 21 = 0
2x(x-3) + 7(x-3) = 0
(2x+7) (x-3) = 0
●2x+7=0 ●x -3 = 0
x= -7/2 x=3
We eliminate -7/2 since the req. no. Is a whole number.
Therefore the answer is 3.
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