If 5x + x² > 100, then x is not
10, 8, 7, 9

Solution:

Given inequality is:

5x + x² > 100

x(5 + x) > 100

If x = 7

7(7 + 5) = 84 which is < 100

If x = 8

5x + x²

x(5 + x)

8(5 + 8) = 104 > 100

If x = 9

5x + x²

x(5 + x)

9(5 + 9) = 126 which is > 100

If x = 10

5x + x²

x(5 + x) = 10(5 + 10) = 150 which is > 100

Therefore 5x + x² > 100 then x is not equal to 7

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If 5x + x² > 100, then x is not 10, 8, 7, 9

Summary:

If 5x + x² > 100, then x is not equal to 7