Mathematics: What is [x + y = -4][x - y =2] solved for elimination ?

What is [x + y = -4][x - y =2] solved for elimination

astra

24.01.2022

Observe that the x coefficients are the same, whereas the y coefficients are opposite. This means that we can use elimation in two ways:

Method 1: SUM

If you sum the two equations, the opposite coefficients will cancel. The sum of the two equations is

$(x+y)+(x-y) = -4+2 \iff 2x=-2 \iff x=-1$

Substitute this value for x in the first equation (for example) and you have

$-1+y=-4 \iff y=-3$

Method 1: SUBTRACT

If you subtract the two equations, the equal coefficients will cancel. The subtraction of the two equations is

$(x+y)-(x-y) = -4-2 \iff -2y=-6 \iff y=-3$

Substitute this value for y in the first equation (for example) and you have

$x-3=-4 \iff x=-1$

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bl6659

04.07.2022

Option d. 75 times.

Step-by-step explanation:

Side length of a square pyramid of Pyramid A = 9 inches

height of pyramid A = 4 inches

$\text{Volume of the squared pyramid}=a^2(\frac{1}{3})h$

where,

a = sides, h = height

$=9^2(\frac{1}{3})\times 4$

$=81(\frac{1}{3})\times 4$

= 27 × 4

= 108 inches³

and the volume of pyramid B = 8100

Now we will divide volume of pyramid B by the volume of pyramid A

$=\frac{8100}{108}$

= 75

Therefore, the volume of pyramid B is 75 times bigger than pyramid A.

Option d is the answer.

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