Jambmaths question:
Solve the inequality ${{x}^{2}}+2x>15$
Option A:
$x<3\text{ or }x>5$
Option B:
$x>3\text{ or }x<-5$
Option C:
$-5<x<3$
Option D:
$x<-3\text{ or }x>5$
Jamb Maths Solution:
${{x}^{2}}+2x>15$
${{x}^{2}}+2x-15>0$
$(x+5)(x-3)>0$
We need to test and find the range of value for this inequality is true
|
|
x < -5 |
-5 < x < 3 |
x > 3 |
|
x + 5 |
– |
+ |
+ |
|
x – 3 |
– |
– |
+ |
|
(x + 5)( x – 3) |
+ |
– |
+ |
The range is x < -5 and x > 3
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