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]
The answer is 30. 2x6 is 12 so you would do 5x6 which is 30
Answer:
D. 25
Step-by-step explanation:
The left end of the baseline has measure (x-16). In this geometry all of the right triangles are similar, so the short-to-long side ratios are proportional:
(x -16)/12 = 12/16
x -16 = 9 . . . . . . . multiply by 12
x = 25 . . . . . . . . . add 16
The unknown length x is 25.
Step-by-step explanation:
x^2=9/49
√x^2=√9/49
x=+or-3/7
(f0g) = -2(x+7)+8
(f0g) = -2x-14+8
(f0g) = -2x-6
(f0g)(2) = -2(2)-6 = -4-6 = -10
(f0g)(2) = -10
hope this helps!
