This is a refreshing question!
We are given that
f(r)=ar+b, and
Sum f(r) =125 for r=1 to 5
Sum f(r) = 475 for r=1 to 10.
and we know, using Gauss's method, that
G(n)=sum (1,2,3.....n) = n(n+1)/2 or
G(n)=n(n+1)/2
Sum f(r) =125 for r=1 to 5
=>
sum=a(sum of 1 to 5) + 5b => G(5)a+5b=125 [G(5)=15]
15a+5b=125 ...................................................(1)
Similarly, Sum f(r) = 475 for r=1 to 10 => G(10)a+5b=475 [G(10)=55]
=>
55a+10b=475.................................................(2)
Solve system of equations (1) and (2)
(2)-2(1)
55-2(15)a=475-2(125) => 25a=225 =>
a=9
Substitute a=9 in 1 => 15(9)+5b=125 => 5b=-10
b=-2
Substitute a and b into f(r),
f(r)=9r-2
check: sum f(r), r=1,5 = (9-2)+(18-2)+(27-2)+(36-2)+(45-2)=135-10=125 [good]
We define the sum of f(r) for r=1 to n as
S(n)=sum f(r) for r=1 to n = 9(sum 1,2,3....n)-2n = 9n(n+1)/2-2n = 9G(n)-2n
S(n)=9n(n+1)/2-2n
checks:
S(5)=9(15)-2(5)=135-10=125 [good]
S(10)=9(55)-2(10)=495-20=475 [good]
Hence
(a)
S(n)=sum f(r) for r=1,n
= 9(sum i=1,n)+n(-2)
= 9(n(n+1)/2 -2n
=(9(n^2+n)/2) -2n
(b) sum f(r) for i=8,18
=sum f(r) for i=1,18 - sum f(r) for i=1,7
=S(18)-S(7)
=(9(18^2-18)/2-2(18))-(9(7^2-7)/2-2(7))
=1503-238
=1265
<h3>
Answer: A. 9</h3>
=====================================================
Explanation:
Draw in the segments AO and OC.
Triangle ABO is congruent to triangle CBO. We can prove this through the use of the HL theorem. HL stands for hypotenuse leg.
Since the triangles are congruent, this means the corresponding pieces AB and BC are the same length.
Then we can say:
AB+BC = AC .... segment addition postulate
AB+AB = AC .... plug in BC = AB
2*AB = AC
2*AB = 18
AB = 18/2 .... divide both sides by 2
AB = 9
In short, the chord AC is bisected by the perpendicular radius drawn in the diagram. So all we do is cut AC = 18 in half to get AB = 9.
Answer:
The greatest common factor of the given expressions is
Step-by-step explanation:
Given that
can be written as
can be written as
and can be written as
Comparing the common factors we have is the greatest common factor of
Therefore the greatest common factor of the given expressions is
Mammals: If the number of Mammal exhibits is 25 and there are 75 total exhibits, the Mammal exhibits are 1/3 of the total exhibits at this Zoo. The ratio for 1/3 is 1:3, which is 25:75 in most complex form. That's 33.3 as a percentage, or 33.3%.
Reptiles: If the number of Reptile exhibits is 15 and there are 75 total exhibits, the reptile exhibits are 1/5 of the total exhibits here. The ratio for 1/5 is 1:5, which is 15:75 fully written out. This as a percentage is 20%.
I'll message you the other half of the answers.