It illustrates distributive property
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:
C) (x - 3)
E) (x - 10)
Step-by-step explanation:
x² - 13x + 30
x² - 10x - 3x + 30
x(x - 10) - 3(x - 10)
(x - 10)(x - 3)
Answer:
y= -2x-7
Step-by-step explanation:
point-slope: y-y1=m(x-x1)
y-3=-2(x-5)
y-3=-2x-10
y=-2x-7
