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How many integers satisfy the inequality $x(3x-4) \le \frac{6x^2 - 3x + 5}{10}$?

 Oct 26, 2014

Best Answer 

 #3
avatar+23254 
+5

x(3x - 4)  ≤  (6x² - 3x + 5) / 10

Simplify:

3x² - 4x  ≤   (6x² - 3x + 5) / 10

30x² - 40x  ≤  6x² - 3x + 5

24x² - 37x - 5  ≤  0

Factoring:  (8x + 1)(3x - 5)  ≤  0

This divides the number line into three parts:  x < -1/8,  -1/8 < x < 5/3,  x > 5/3

Try a a number in the lower region:  I tried -1:  [8(-1) + 1][3(-1) - 5]  =  56. Since this is not less than or equal to zero, all numbers less than -1/8 will not work.

Try a number in the middle region:  I tried 0:  [8(0) + 1][3(0) - 5]  =  -5. Since this is less than zero, all numbers in this region work.    Answer:  -1/8 < x < 5/3

Try a a number in the upper region:  I tried 2:  [8(2) + 1][3(2) - 5]  =  17. Since this is not less than or equal to zero, all numbers greater than 5/3 will not work.

Now, to answer the question, you will have to figure out (count) the number of integers in the region 

-1/8 < x < 5/3.

- See more at: http://web2.0calc.com/questions/help-please_45#sthash.fDB7TCoS.dpuf

 Oct 26, 2014
 #3
avatar+23254 
+5
Best Answer

x(3x - 4)  ≤  (6x² - 3x + 5) / 10

Simplify:

3x² - 4x  ≤   (6x² - 3x + 5) / 10

30x² - 40x  ≤  6x² - 3x + 5

24x² - 37x - 5  ≤  0

Factoring:  (8x + 1)(3x - 5)  ≤  0

This divides the number line into three parts:  x < -1/8,  -1/8 < x < 5/3,  x > 5/3

Try a a number in the lower region:  I tried -1:  [8(-1) + 1][3(-1) - 5]  =  56. Since this is not less than or equal to zero, all numbers less than -1/8 will not work.

Try a number in the middle region:  I tried 0:  [8(0) + 1][3(0) - 5]  =  -5. Since this is less than zero, all numbers in this region work.    Answer:  -1/8 < x < 5/3

Try a a number in the upper region:  I tried 2:  [8(2) + 1][3(2) - 5]  =  17. Since this is not less than or equal to zero, all numbers greater than 5/3 will not work.

Now, to answer the question, you will have to figure out (count) the number of integers in the region 

-1/8 < x < 5/3.

- See more at: http://web2.0calc.com/questions/help-please_45#sthash.fDB7TCoS.dpuf

geno3141 Oct 26, 2014

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