Solve the system using elimination. x − 4y = 4
3x − 4y = −12

A. (−2,112)

B. (−8,−3)

C. (−8,9)

D. (−2,−112)

B. (-3,-8)

Step-by-step explanation:

I have aced tests on these. You can trust this is correct - plus it's verified by a calculator.

B

Step-by-step explanation:

x - 4y = 4 → (1)

3x - 4y = - 12 → (2)

Multiplying (1) by - 1 and adding to (2) will eliminate the y- term

- x + 4y = - 4 → (3)

Add (2) and (3) term by term to eliminate y

2x + 0 = - 16

2x = - 16 ( divide both sides by 2 )

x = - 8

Substitute x = - 8 into either of the 2 equations and solve for y

Substituting into (1)

- 8 - 4y = 4 ( add 8 to both sides )

- 4y = 12 ( divide both sides by - 4 )

y = - 3

solution is (- 8, - 3 ) → B

let's call the solutions x₁ = (5 - 2√7)/3 and x₂ = (5 + 2√7)/3

then the equation is (x-x₁)(x-x₂) = 0

if you fill that in you get a lot of numbers which you can recognize as ax²+bx+c=0.

step-by-step explanation:

you can see that a=1 (there is just an x²)

b = (-5 -2√7 + 2√7 - 5)/3 = -10/3

c = -2√7)/3 ) * (-5+2√7)/3) = -1/3

so your answer is 3x^2 – 10x – 1 = 0