If z² - 4z > 5 then which of the following is always true
A) z > -5
B) z < 5
C) z > -1
D) z < 1
E) z < -1
Ans:E
But i feel the answer is c.somebody pls explain
z² - 4z > 5
This topic has expert replies
It looks like this:
(x-5)(x+1)>0
There are 2 possible outcomes for this to be true.
1. X-5>0 X> 5
x+1>0 x>-1 So X must be greater than 5 , as it includes both intervals.
2. X-5<0 X<5
x+1<0 x<-1 X must be less than -1 to include both intervals....
So if you choose from your answer choices the correct answer is E. X must be less than -1.... another possible answer could be X >5 ... but it is not included in answers.
Hope it helps.
(x-5)(x+1)>0
There are 2 possible outcomes for this to be true.
1. X-5>0 X> 5
x+1>0 x>-1 So X must be greater than 5 , as it includes both intervals.
2. X-5<0 X<5
x+1<0 x<-1 X must be less than -1 to include both intervals....
So if you choose from your answer choices the correct answer is E. X must be less than -1.... another possible answer could be X >5 ... but it is not included in answers.
Hope it helps.
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Thanks for your replies.
but i tried to solve like this:
(z-5)(z+1)>0
equating (z-5)>0 we get z>5
equating (z+1)>0 we get z>-1
so i chose C.
I want to know what went wrong in my calculation.
need your assistance :roll:
but i tried to solve like this:
(z-5)(z+1)>0
equating (z-5)>0 we get z>5
equating (z+1)>0 we get z>-1
so i chose C.
I want to know what went wrong in my calculation.
need your assistance :roll:
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You need to look at the common solution that will satisfy the inequality.
so if (Z-5)(Z+1) > 0,. then the area covering Z - 5 >0 and Z+1 > 0 or Z- 5 < 0 and Z+1<0 will satisfy the inequality.
Now if we choose Z - 5 > 0 and Z + 1 > 0 then the common area that satisfies this equation is z> 5 as represented below on the number line.
------|{-----------|---------------|{------------
-1 0 5
The common area that satisfies the equation is Z > 5
so if (Z-5)(Z+1) > 0,. then the area covering Z - 5 >0 and Z+1 > 0 or Z- 5 < 0 and Z+1<0 will satisfy the inequality.
Now if we choose Z - 5 > 0 and Z + 1 > 0 then the common area that satisfies this equation is z> 5 as represented below on the number line.
------|{-----------|---------------|{------------
-1 0 5
The common area that satisfies the equation is Z > 5
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z(z-4)>5iikarthik wrote:If z² - 4z > 5 then which of the following is always true
A) z > -5
B) z < 5
C) z > -1
D) z < 1
E) z < -1
z(z-4)-5>0
-------------------|---------------|-----------
z=-1 no, -2 ok 0 for z=2, -4 4 for z=5, 5no, for z=6 12 yes
so for z<-1 z(z-4) will be always greter than 5 E is indeed corect
for z>-1 means somewhere right side z>0 which is incorrect
Charged up again to beat the beast