strictly concave up function

suppose that f : R-->R is strictly concave up, strictly increasing function with a zero t satisfying a<t< b
Which of the following are true
1.f(b)<0
2.f(b)=0
3.f(b)>0
4.f(a)<0
5.f(a)=0
6.f(a)>0
7.impossible to determine

can someone help me with this

I would feel better about answering if you had shown some attempt yourself!

Consider the function with
i) a= 0, b= 2
ii) a= -2, b= 0

i don't understand what i'm supposed to do

Quote:

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Originally Posted by dat1611

suppose that f : R-->R is strictly concave up, strictly increasing function with a zero t satisfying a<t< b
Which of the following are true
1.f(b)<0
2.f(b)=0
3.f(b)>0
4.f(a)<0
5.f(a)=0
6.f(a)>0
7.impossible to determine

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Do you know what a strictly increasing function means?

upward sloping i think not sure what zero t means

Quote:

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Originally Posted by dat1611

upward sloping i think not sure what zero t means

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f(x) is a strictly increasing function. that tells you that if a < t < b , then f(a) < f(t) < f(b)

"zero t" means f(t) = 0

ok so...
1.f(b)<0 false
2.f(b)=0 false
3.f(b)>0 true
4.f(a)<0 true
5.f(a)=0 false
6.f(a)>0 false