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.
815.755 round to the nearest hundred is 816
Answer:
1.31, 0.19 to nearest hundredth.
Step-by-step explanation:
1/x + 1/(x - 1) = 4
Multiply through by x(x - 1):-
x - 1 + x = 4x(x - 1)
4x^2 - 4x = 2x - 1
4x^2 - 6x = -1
4(x^2 - 3.2 x) = -1
Completing the square:-
4 [ ( x - 3/4)^2 - 9/16] = -1
4(x - 3/4)^2 - 9/4 = -1
4(x - 3/4)^2 = 5/4
(x - 3/4)^2 = 5/16
x - 3/4 = +/- √5 / 4
x = √5 / 4 + 3/4 , -√5 / 4 + 3/4
= 1.31, 0.19 to nearest hundredth.
Answer:
yes your right buddy
Step-by-step explanation:
Answer:
x=15 and y=18
Step-by-step explanation:
1: 2/3x- 4=6 2/3x=10 x=15
1: x=15
2: 2/3y=12
y=18
