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]
Answer:
3a5a2b
Step-by-step explanation:
You can prime factorize 15: 3 x 5
Answer:
Angle A
Step-by-step explanation:
a is greater than b, which is greater than c
a triangle has 180 degrees
so 180-90 is 90
90-60 is 30
a>b>c
90>60>30
this would be a right triangle since one of the angles is 90 degrees
Answer:
Bottle unit: 8.14
Dollar unit: $0.12
Step-by-step explanation:
Dividing the equation, bottle on top for bottle and dollars on top for dollar.
