Answer:A
Step-by-step explanation:
-8=a(2+5)^2 + 41
-8=a x 7^2 + 41
-8=a x 7 x 7 +41
-8=49a+41
Collect like terms
-8-41=49a
-49=49a
Divide both sides by 49
-49/49=49a/49
-1=a
a=-1
First term ,a=4 , common difference =4-7=-3, n =50
sum of first 50terms= (50/2)[2×4+(50-1)(-3)]
=25×[8+49]×-3
=25×57×-3
=25× -171
= -42925
derivation of the formula for the sum of n terms
Progression, S
S=a1+a2+a3+a4+...+an
S=a1+(a1+d)+(a1+2d)+(a1+3d)+...+[a1+(n−1)d] → Equation (1)
S=an+an−1+an−2+an−3+...+a1
S=an+(an−d)+(an−2d)+(an−3d)+...+[an−(n−1)d] → Equation (2)
Add Equations (1) and (2)
2S=(a1+an)+(a1+an)+(a1+an)+(a1+an)+...+(a1+an)
2S=n(a1+an)
S=n/2(a1+an)
Substitute an = a1 + (n - 1)d to the above equation, we have
S=n/2{a1+[a1+(n−1)d]}
S=n/2[2a1+(n−1)d]
Hello,
h(x)= if x<3 then x+2
else -x+8
(–∞5[ U [5 –∞)=(–∞ 5]
Answer B
Answer:
$356
Step-by-step explanation:
So if they are 400 students we need to:
0.89*400=$356
