Answer:
Sum of the first 15 terms = -405
Step-by-step explanation:
a + 3d = -15 (1)
a + 8d = -30 (2)
Where,
a = first term
d = common difference
n = number of terms
Subtract (1) from (1)
8d - 3d = -30 - (-15)
5d = -30 + 15
5d = -15
d = -15/5
= -3
d = -3
Substitute d = -3 into (1)
a + 3d = -15
a + 3(-3) = -15
a - 9 = -15
a = -15 + 9
a = -6
Sum of the first 15 terms
S = n/2[2a + (n − 1) × d]
= 15/2 {2×-6 + (15-1)-3}
= 7.5{-12 + (14)-3}
= 7.5{ -12 - 42}
= 7.5{-54}
= -405
Sum of the first 15 terms = -405
Answer:
F(2)= 10 or C
Step-by-step explanation:
You just need to plug the answers in.
F(x)=3x+4
--
f(2)=3(2)+4
f(2)=6+4
f(2)= 10
We just have to solve to get a simplified answer
we have
9y + 5 = 7 + 3y + 2y
9y +5 = 7 + 5y
9y-5y= 7-5
4y=2
so if we solve further we will not get the answer that is given in option
so option d is the write answer
