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:
When we think of World War I, images of the bloody, muddy Western Front are generally what come to mind. Scenes of frightened young men standing in knee-deep mud, awaiting the call to go "over the top", facing machine guns, barbed wire, mortars, bayonets, hand-to-hand battles, and more. We also think of the frustrations of all involved: the seemingly simple goal, the incomprehensible difficulty of just moving forward, and the staggering numbers of men killed. The stalemate on the Western Front lasted for four years, forcing the advancement of new technologies, bleeding the resources of the belligerent nations, and destroying the surrounding countryside. I've gathered photographs of the Great War from dozens of collections, some digitized for the first time, to try to tell the story of the conflict, those caught up in it, and how much it affected the world. This entry is part 2 of a 10-part series on World War I. This installment focuses on Early Years on the front, part II will focus more on the final year of trench warfare.
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Step-by-step explanation:
Answer:
go on symbolab type the equation in and it gives u anwsers and work
Step-by-step explanation:
=\frac{4}{\left(x+2\right)\left(x+4\right)}
You must first attach the problems with your question.
Answer:
∠AMB = 54°
Step-by-step explanation:
2x + (x + 9) = 90°
3x + 9° = 90°
3x = 81°
x = 27°
∠AMB = 2x = 54°
