General formula for n-th term of arithmetical progression is
a(n)=a(1)+d(n-1).
For 3d term we have
a(3)=a(1) +d(3-1), where a(3)=7
7=a(1)+2d
For 7th term we have
a(7)=a(1) +d(7-1)
a(7)=a(1) + 6d
Also, we have that the <span>seventh term is 2 more than 3 times the third term,
a(7)=3*a(3)+2= 3*7+2=21+2=23
So we have, </span>a(7)=a(1) + 6d and a(7)=23. We can write
23=a(1) + 6d.
Now we can write a system of equations
23=a(1) + 6d
<span> - (7=a(1)+2d)
</span>16 = 4d
d=4,
7=a(1)+2d
7=a(1)+2*4
a(1)=7-8=-1
a(1)= - 1
First term a(1)=-1, common difference d=4.
Sum of the 20 first terms is
S=20 * (a(1)+a(20))/2
a(1)=-1
a(n)=a(1)+d(n-1)
a(20) = -1+4(20-1)=-1+4*19=75
S=20 * (-1+75)/2=74*10=740
Sum of 20 first terms is 740.
Answer:
5.3x^3+11.1x+0.8
Step-by-step explanation:
Add ones with similar variables
5.3x^3+11.1x+0.8
Answer:
-3, 5/2
Step-by-step explanation:
What are the roots of the function y = 4x2 + 2x – 30?
To find the roots of the function, set y = 0. The equation is 0 = 4x2 + 2x – 30.
Factor out the GCF of : 2, so the equation becomes 0 = 2(2x2+x-15)
Next, factor the trinomial completely. The equation becomes: 0=2(x+3)(2x-5)
Use the zero product property and set each factor equal to zero and solve.
x+3=0 2x-5 = 0
x = -3, 5/2
The roots of the function are -3, 5/2.
Hope this helped!
Answer:
Okay you are asking for the area of a circle ( drum head ) to find that is. You get R (radious) by dividing 14 by 2 and get 7
Step-by-step explanation:
A= πr^2
so what is the R? Its 7
Plug the numbers in and
and your answer is 153.94
