4x + 5y = 7 and 8x + 5y = 9 * Elimination

Mathematics

2 answers:

Luden [163]3 years ago

7 0

Answer:

Solve equation [2] for the variable y

[2] y = 8x + 7

// Plug this in for variable y in equation [1]

[1] 4x - 5•(8x+7) = -9

[1] -36x = 26

// Solve equation [1] for the variable x

[1] 36x = - 26

[1] x = - 13/18

// By now we know this much :

x = -13/18

y = 8x+7

// Use the x value to solve for y

y = 8(-13/18)+7 = 11/9

Solution :

{x,y} = {-13/18,11/9}

bazaltina [42]3 years ago

4 0

It should be y=2 after you eliminate

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3 years ago

How much cardboard is needed to make the tissue box above? Square inches 8 3 3

Katen [24]

The amount of cardboard needed to make a cuboid box of dimensions 8 inch, 3 inches and 3 inches is 114 sq. inches.

<h3>What is the surface area of cuboid?</h3>

Let the three dimensions(height, length, width) be x, y,z units respectively.

The surface area of the cuboid is given by

$S = 2(a\times b + b\times c + c\times a)$

For this case, tissue box is almost cuboid shaped.

Also, its dimensions are given being 8 inches, 3 inches and 3 inches.

Suppose we measure the amount of cardboard needed in terms of area, then, the amount of cardboard needed to make that box(without any whole, full cuboid) is equal to the area of its surface(either outer or inner if we assume 0 inches thickness of cardboard),

Thus, we get:

Amount of cardboard needed = surface area of cuboid box with dimensions 8 by 3 by 3 (in inches)

= $2(8 \times 3 + 3 \times 3 + 3 \times 8) = 114 \: \rm in^2$