The second one is the correct answer
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:
2. 
Step-by-step explanation:
We have been given an expression 
and we are asked to find equivalent expression to our given expression.
Using fraction rule 
we can write our expression as: 
.
Upon dividing 10 by 5 we will get,
Upon using exponent property for quotient 
we will get,
Therefore, our expression simplifies as and 2nd option is the correct choice.
Answer: The answer is 49 because 128-79=49
Answer:
8!=40320
Step-by-step explanation:
SInce their are 8 athletes and 8 positions we can assume this: The first sprinter has 8 positions to end in, the next has 7 places to finish in, the third has 6 places and so on... Using this we can multiply these possibilities to find that the possibilities are 8×7×6×5×4×3×2 which results in 40320 (this function is known as a factorial and denoted !).
