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surabi · 09-06-2002, 03:50 PM

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

The equation can be written as z² - 4z - 5 > 0. . . (z - 5)(z + 1) > 0. If we set it equal to zero we find z > 5, z > -1. right?....
But the explanation given to this says z>5 and Z<-1 ..how is this?..I think i have some problem with solving these inequalities. Some one please help me.
The aswer is E

09-06-2002, 03:50 PM	#1 (permalink)
surabi Trying to make mom and pop proud Join Date: Jun 2002 Location: USA Posts: 5	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 The equation can be written as z² - 4z - 5 > 0. . . (z - 5)(z + 1) > 0. If we set it equal to zero we find z > 5, z > -1. right?.... But the explanation given to this says z>5 and Z<-1 ..how is this?..I think i have some problem with solving these inequalities. Some one please help me. The aswer is E