Question

Solve the Equation
3x+2y=17
-2x-y=-12

Answer 1

x = 7, y = -2

Explanation:

`\left\{\begin{array}{ccc}3x+2y=17&(1)\\-2x-y=-12&(2)\end{array}\right\\\\(2)\\-2x-y=-12\qquad\text{add 2x to both sides}\\-y=2x-12\qquad\text{change the signs}\\y=-2x+12\qquad\text{substitute it to (1):}\\\\3x+2(-2x+12)=17\qquad\text{use the distributive property}\ a(b+c)=ab+ac\\3x+(2)(-2x)+(2)(12)=17\\3x-4x+24=17\qquad\text{subtract 24 from both sides}\\-x=-7\qquad\text{change the signs}\\\boxed{x=7}\\\\\text{Put the value of x to (2):}\\\\y=-2(7)+12\\y=-14+12\\\boxed{y=-2}`

Answer 2

(7,-2)

Explanation:

3x+2y=17

-2x-y=-12

Multiply the second equation by 2 so we can eliminate y

2( -2x-y=-12) becomes -4x-2y = -24

Add this to the first equation

3x+2y=17

-4x-2y=-24

----------------

-x = -7

Multiply each side by -1

x = 7

Substitute back into the first equation to find y

3(7) +2y = 17

21 +2y = 17

Subtract 21 from each side

21-21 +2y = 17-21

2y = -4

Divide each side by 2

2y/2 = -4/2

y =-2

(7,-2)