What is the solution to the system of equations?
x = -4y
3x + 2y = 20

(x, y) = (8, -2)

Step-by-step explanation:

Substitute:

3(-4y) + 2y = 20

-12y + 2y = 20

-10y = 20

y = -2

x = -4(-2) = 8

(8,-2)

Step-by-step explanation:

x=-4y

3x+2y=20

3(-4y)+2y=20

Multiply (distribute)

-12y+2y=20

-10y=20

Divide both sides by -10

y=-2

x=-4(-2)

x=8

- 2 + 10x³ - 21x² + 19x - 4

step-by-step explanation:

each term in the second factor is multiplied by each term in the first factor

x²(- 2x² + 4x - 1) - 3x(- 2x² + 4x - 1) + 4(- 2x² + 4x - 1) ← distribute

= - 2 + 4x³ - x² + 6x³ - 12x² + 3x -8x² + 16x - 4

collect like terms

= - 2 + 10x³ - 21x² + 19x - 4 ← in standard form

a 4/6 = 9/12   not proportional

step-by-step explanation:

to find which are not proportional, we can use cross products

if it is true, they are proportional.   if it is not true, they are not proportional.

a 4/6 = 9/12

4* 12 = 6*9

48 = 54

not this is not proportional  

b 2/3 = 12/18  

2* 18 = 3 * 12

36 = 36

this is proportional

c 5/4 = 10/8  

5*8 = 4*10

40 = 40

this is proportional

d 7/5 = 35/25

7*25 = 5 * 35

175 = 175

is proportional