Solve 3x+2y=7 and x-4y=-21 by using any method

(- 1, 5 )

Step-by-step explanation:

Using the method of substitution.

Given the 2 equations

3x + 2y = 7 → (1)

x - 4y = - 21 → (2)

Rearrange (2) expressing x in terms of y by adding 4y to both sides.

x = 4y - 21 → (3)

Substitute x = 4y - 21 into (1)

3(4y - 21) + 2y = 7 ← distribute and simplify left side

12y - 63 + 2y = 7

14y - 63 = 7 ( add 63 to both sides )

14y = 70 ( divide both sides by 14 )

y = 5

Substitute y = 5 into (3)

x = (4 × 5) - 21 = 20 - 21 = - 1

Solution is (- 1, 5 )

b

step-by-step explanation:

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