math
8th Grade - Inequalities

8th Grade lesson

3 - Inequalities


You know how to solve an inequality (inequality solving, 7th Grade lesson).

Now instead of the sign =, there is either < or >. You can solve this kind of inequality the same way as seen in the 7th Grade lesson. The only difference is situated in the third example.
2x + 2 < 4
2x < 4 - 2
2x < 2
x < 2 2
x < 1
9x - 9 < 54
9x < 54 + 9
9x < 63
x < 63 9
x < 7
3x + 3 < 6x + 6
3x - 6x < 6 - 3
-3x < 3
x > 3(-3)
x > 1
Have you noticed? When you divide by a negative number, the inequality is reversed. Its the same thing if you multiply with a negative number. For example, you have known since you were a child that 2<3 (at last something you understand!). Multiply both sides by -10, it makes -20 and -30. Its -30 which is the smallest, that's why you have to change the inequality sign (-20>-30).

2x + 4 > 4x - 16
2x - 4x > -16 - 4
-2x > -20
x < (-20)(-2)
x < 10

A last example that you must understand and it will be OK.

inequality solving
inequality solving
inequality solving
inequality solving
inequality solving
inequality solving
inequality solving
inequality solving
inequality solving




See also : algebra on fmaths.com



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inequalities

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