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3 years ago

13. If 6 times the 6th term of an A.P. is equal to

Mathematics

1 answer:

romanna [79]3 years ago

7 0

Answer:

see explanation

Step-by-step explanation:

The n th term of an AP is

$a_{n}$ = a₁ + (n - 1)d

where a₁ is the first term and d the common difference

Given

6(a₁ + 5d) = 13(a₁ + 12d) ← distribute parenthesis on both sides

6a₁ + 30d = 13a₁ + 156d ( subtract 13a₁ from both sides )

- 7a₁ + 30d = 156d ( subtract 30d from both sides )

- 7a₁ = 126d ( divide both sides by - 7 )

a₁ = - 18d

Now

a₁₉ = a₁ + 18d = - 18d + 18d = 0 ← as required

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Answer:

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1. What is the value of the y variable in the solution to the following system of equations?

ollegr [7]

Part 1)

we have

$3x-6y=3$ ------> equation A

$7x-5y=-11$ ------> equation B

Multiply by $-7$ the equation A

$-7(3x-6y)=-7*3$

$-21x+42y=-21$ ------> equation C

Multiply by $3$ the equation B

$3*(7x-5y)=-11*3$

$21x-15y=-33$ -------> equation D

Adds equation C and equation D

$-21x+42y=-21 \\21x-15y=-33\\---------- \\ 42y-15y=-21-33\\27y=-54 \\ y=-2$

therefore

the answer Part 1) is the option A

$y=-2$

Part 2)

we have

$3x+y=6$

$y=-3x+6$ ------> equation A

$6x+2y=8$

Simplify Divide by $2$ both sides

$3x+y=4$

$y=-3x+4$ ------> equation B

the lines A and B are parallel lines, because the slope m is equal

The system has no solution

therefore

the answer Part 2) is the option D

There is no x value as there is no solution to the system.

Part 3)

we have

$4x+2y=6$ ------> equation A

$x-y=3$

$y=x-3$ ------> equation B

substitute equation B in equation A

$4x+2[x-3]=6$

$6x-6=6$

$6x=12$

$x=2$

therefore

the answer part 3) is the option D

$x=2$

Part 4)

Let

x---------> The number of one-step equations

y---------> The number of two-step equations

we know that

$x+y=1,120$

$x=1,120-y$ -------> equation A

$3x-2y=1,300$ ------> equation B

substitute equation A in equation B

$3[1,120-y]-2y=1,300$

$3,360-5y=1,300$

$5y=3,360-1,300$

$5y=2,060$

$y=412$

therefore

the answer part 4) is the option D

$y=412$

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Gina has 1200 yards of fencing to enclose a rectangular area. Find the dimensions of the rectangle that maximize the enclosed ar

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We know the perimeter formula would be 1200=2x+2y. And the area will be A=x*y
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Now we take the derivative:
A'=600-2x (set equal to 0 and solve)
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Then when we plug this into the perimeter formula, we can solve for y
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600=2y
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So both the length and width are 300 yards, and the area would be 90,000 square yards

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