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# Solve the system of equations using the substitution method. Please Help!

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1. y = 2x^2 + x - 1

y = -x - 3

2. y = -2x^2 - 2x + 3

y = 7/2

Apr 17, 2018
edited by GAMEMASTERX40  Apr 17, 2018

### Best Answer

#1
+1

Substituting y = - x - 3 into the first equation, we have:

- x - 3 = 2 x ^ 2 + x -1

Simplifying, we have:

2 x ^ 2 + 2 x + 2 = 0

x=-\frac{1}{2}+i\frac{\sqrt{3}}{2},\:x=-\frac{1}{2}-i\frac{\sqrt{3}}{2}

Substituting y = 7/2 into the first equation, we have:

7/2  = - 2 x ^ 2 - 2 x + 3

Simplifying, we have:

2 x ^ 2 + 2 x + 2 = 0

x=-\frac{1}{2}

Since you already know one value, you can plug it in to figure out the other variable.

Apr 17, 2018

### 1+0 Answers

#1
+1
Best Answer

Substituting y = - x - 3 into the first equation, we have:

- x - 3 = 2 x ^ 2 + x -1

Simplifying, we have:

2 x ^ 2 + 2 x + 2 = 0

x=-\frac{1}{2}+i\frac{\sqrt{3}}{2},\:x=-\frac{1}{2}-i\frac{\sqrt{3}}{2}

Substituting y = 7/2 into the first equation, we have:

7/2  = - 2 x ^ 2 - 2 x + 3

Simplifying, we have:

2 x ^ 2 + 2 x + 2 = 0

x=-\frac{1}{2}

Since you already know one value, you can plug it in to figure out the other variable.

GYanggg Apr 17, 2018