SOLUTION: Twice the square of an integer is 21 more than eleven times the integer. Find the integer.

Question 144460: Twice the square of an integer is 21 more than eleven times the integer. Find the integer.
Answer by Alan3354(69443) (Show Source): You can put this solution on YOUR website!

Solved by pluggable solver: SOLVE quadratic equation (work shown, graph etc)

Quadratic equation (in our case ) has the following solutons:

For these solutions to exist, the discriminant should not be a negative number.

First, we need to compute the discriminant : .

Discriminant d=289 is greater than zero. That means that there are two solutions: .

Quadratic expression can be factored:

Again, the answer is: 7, -1.5. Here's your graph:

-1.5 is not an integer, so the answer is 7.
2 times 7 times 7 = 11 times 7 + 21

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