solve quadratic by taking square roots. as=a,-a where a and -a the values you found when when solving. Round to nearest tenth. 2x^2-9=121

8.1

Step-by-step explanation:

2x^2 -9 = 121

        +9    +9

2x^2 = 130

/2         /2

x^2   = 65

x= sqrt (65)

x= 8.06225...

x = 8.1

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