Algebraic Method α€€ိုα€žံုးα€™α€š္ဆိုရင္ ေထာα€€္ပါေပးထားတဲ့ logical rule α€€ို α€žိရပါα€™α€š္။

(i) ab>0 then there are two different possibilities that

(ii) Similarly, for ab<0 the possibilities may be

(i)ab>0 ဆိုα€žα€Š္α€™ွာ a ႏွင့္ b ေျα€™ႇာα€€္ျခင္း α€žα€Š္ ထေပါင္းတန္α€˜ိုး ျα€–α€…္α€žα€Š္။ ထိုα€žိုα‚”ျα€–α€…္α€›α€”္ a ႏွင့္ b α€žα€Š္ ထေပါင္းတန္α€˜ိုး ျα€–α€…္α€›α€™α€Š္။ α€žိုα‚”α€™α€Ÿုတ္ a ႏွင့္b ႏွα€…္ခုα€œံုးα€žα€Š္ ထႏႈတ္တန္α€˜ိုး ျα€–α€…္α€›α€™α€Š္။

(ii) ab<0 ဆိုα€žα€Š္α€™ွာ a ႏွင့္ b ေျα€™ႇာα€€္ျခင္း α€žα€Š္ ထႏႈတ္တန္α€˜ိုး ျα€–α€…္α€žα€Š္။ ထိုα€žိုα‚”ျα€–α€…္α€›α€”္ a α€žα€Š္ ထေပါင္းတန္α€˜ိုးα€Ÿု α€šူα€†α€œွ်င္ b α€žα€Š္ ထႏႈတ္တန္α€˜ိုး ျα€–α€…္α€›α€™α€Š္။ α€žိုα‚”α€™α€Ÿုတ္ a α€žα€Š္ ထႏႈတ္တန္α€˜ိုးα€Ÿု α€šူα€†α€œွ်င္ b α€žα€Š္ ထေပါင္းတန္α€˜ိုး ျα€–α€…္α€›α€™α€Š္။

Example 1
Use algebraic method, to find the solution set of the inequation 12 - 5x - 2x2 ≥ 0 and illustrate it on the number line.

http://i627.photobucket.com/albums/tt352/Thu-Rein/template/th_bluearrow.gifSolution
12 - 5x - 2x2 ≥ 0
(4 + x)(3 - 2x) 0
ထထက္တြင္ ေα€–αšျပခဲ့ေα€žာ rule(i)α€€ို α€žံုး၍ ေျα€–α€›ွင္းပါα€™α€Š္။

There are two possibilities for (4 + x)(3 - 2x) 0

(i)(4 + x) 0 and (3 - 2x) 0
x -4 and x 3/2
ႏွα€…္α€™်ိဳးα€œံုးα€€ိုα€šူα€›α€”္α€™α€œို၊ ထေျခထေα€” ႏွα€…္ရပ္α€œံုးα€€ို ေျα€•α€œα€Š္ေα€…ေα€žာ ထေျဖတစ္ခုα€€ိုα€žာ α€šူα€™α€Š္။ α€™α€Š္α€žα€Š္α€€ို α€šူα€™α€Š္ ဆိုα€žα€Š္α€€ို number line ဆြဲ၍ α€…α€₯္းα€…ားႏိုင္α€žα€Š္။


ထေျခထေα€” ႏွα€…္ရပ္α€œံုးတြင္ α€˜ံုျα€–α€…္ေα€žာ
-4 ≤ x ≤ 3/2α€€ိုα€žာ α€šူပါα€™α€Š္။




(ii)(4 + x) 0 and (3 - 2x) 0
x -4 and x 3/2
ထထက္ပါα€”α€Š္းထတိုင္း number line ဆြဲ၍ α€…α€₯္းα€…ားα€™α€Š္။

ထေျခထေα€” ႏွα€…္ရပ္α€œံုးတြင္ ေျα€•α€œα€Š္ေα€…ေα€žာ α€˜ံုထေျα€– α€™α€›ွိပါ။




The solution set of 12 - 5x - 2x2 ≥ 0 is {x/-4 ≤ x ≤ 3/2}.




Example 2

Find the solution set of the inequation 12x2 10 - 7x by graphical method and illustrate it on the number line.

http://i627.photobucket.com/albums/tt352/Thu-Rein/template/th_bluearrow.gifSolution
12x2 10 - 7x
12x2 + 7x - 10 0
(4x + 5)(3x - 2)
0
There are two possibilities for (4 + x)(3 - 2x) 0
(i)
(4x + 5) 0 and (3x - 2) 0
Therefore x
≥ - 5/4 and x ≥ 2/3


The solution which satisfies both conditions is
x ≥ 2/3.





(ii)(4x + 5)
0 and
(3x - 2)
0
Therefore x
- 5/4 and
x
2/3

The solution which satisfies both conditions is
x
- 5/4.





The solution set of 3x2 < x2 - x + 3 is {x/ x - 5/4 or x 2/3}.