Mark is solving the following system (1)
X+ y + z = 2
3x+2y + Z = 8
4x-y-73= 16
(2)
(3)
Step 1: He multiplies equation (1) by 7 and adds it to equation (3)
Step 2: He multiplies equation (3) by 2 and adds it to equation (2)
Which statement explains Mark's mistake?

b

step-by-step explanation:

the word superfluous means unnecessary

answer for #1 is c

answer for #2 is d

can i get brainliest

x = ±sqrt(10)

step-by-step explanation:

5 - 2x² = -15

subtract 5 from each side

5-5 - 2x² = -15-5

-2x^2   = -20

divide by -2 on each side

-2x^2   /-2= -20/-2

x^2 =10

take the square root on each side

sqrt(x^2 )=±sqrt(10)

x = ±sqrt(10)

check:

5 - 2x² = -15

+sqrt(10)

5 - 2(sqrt(10))² = -15

5 -2(10) = -15

5 -20 = -15

-15 = -15

-sqrt(10)

5 - 2(-sqrt(10))² = -15

5 -2(10) = -15

5 -20 = -15

-15 = -15

it would open into a square depending on the type of envelope i’m not sure about the second part