Answer:
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Step-by-step explanation:
a₁ = 1
a₂ = 8 = 1 + 7 = a₁ + 7
a₃ = 15 = 1 + 7 + 7 = a₁ + 7×2
a₄ = 22 = 1 + 7 + 7 + 7 = a₁ + 7×3
Therefore:
Everyone should do this derivation, because otherwise the "quadratic formula" is some sort of "magic" LOL...
ax^2+bx+c=0
x^2+bx/a+c/a=0
x^2+bx/a=-c/a
x^2+bx/a+b^2x/(4a^2)=b^2/(4a^2)-c/a
(x+b/(2a))^2=(b^2-4ac)/(4a^2)
x+b/(2a)=±√(b^2-4ac)/(2a)
x=-b/(2a)±√(b^2-4ac)/(2a)
x=(-b±√b^2-4ac)/(2a)
Hey there!
Formula for area of an octagon:
A = 2(1 + √2)a²
The variable a is side length.
Plug in 13 for a.
A = 2(1 + √2)13²
Simplify.
A = 2(1 + √2)169
A = 338(1 + √2)
A = 816 ft²
Hope this helps!
Answer:
50 7th grade and 40 8th grade
Step-by-step explanation:
1. add to get total number of students, 1440
2. find percentage of total that are 7th grade students and 8th grade student:
640/1440 = ~45% (are 7th grade)
800/1440 = ~55% (are 8th grade)
3. 55% of 90 is 50, and 45% of 90 is 40