Factor completely 2x2 − 2x − 40
A. 2(x − 5)(x + 4)
B. (2x − 10)(x + 4)
C. (x − 5)(2x + 8)
D. 2(x − 4)(x + 5)

2(x-5)(x+4)

Step-by-step explanation:

2x^2 − 2x − 40

Factor out a 2

2(x^2 -x -20)

What 2 numbers multiply to -20 and add to -1

-5*4 = -20

-5+4 = -1

2(x-5)(x+4)

x = -3

y = -18

step-by-step explanation:

to solve by substitution, substitute one variable and solve for the other. then substitute again to find the remaining variable.

x-1/3(3x-9) = -3 since y=3x-9 substittute y.

x-1/3(3x-9)=-3

x + x +3 = -3

2x+3=-3

2x+3-3= -3-3

2x=-6

x=-3

substitute again into y=3x-9

y=3(-3)-9

y=-9-9

y=-18