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:
72 +1 , If u = A 8 1 - 2 ( ( + + +1 )– flog ( 3 + 3 / 3 ) ? v1m * + n + 13 ) 4 1 ; then 2 If c ... of any number of such MATHEMATICS . triangles ; and ( 3 ) find the mean value of ... 72 = 62 + 69 , 73 = 82 + 39 , 75 = 72 + 52 . the in - centre and centroid . ... 4n + 1 , or 4n + 2 ,
Step-by-step explanation:
25% = 85 / 4 = $21.25 off
5% = 85 / 20 = $4.25
75% = 21.25 • 3 = $63.75
$63.75 + $4.25 = $68
Her total bill was $68
Answer:
B
Step-by-step explanation:
Remark
I have to represent f(x) as plus +f(x)
I like to show this situation as +f(g(x)) which I think is much clearer.
+f(x) = 5x - 4
Solution
+f(g(x)) = 5(g(x)) - 4 What has happened is that wherever you see an x on the right you put in g(x).
Now on the right, you put whatever g(x) is equal to.
+f(g(x)) = 5(x^2 - 1) - 4
Remove the brackets.
+f(g(x)) = 5x^2 - 5 - 4
And make x = 0
+f(g(0)) = 5*0 - 5 - 4
+f(g(0)) = - 9
