Question

If 3x-y=5 and 2x+y= 15, evaluate x^2+2yx​

Answer 1

72

Explanation:

3x-y=5

2x+y= 15

Adding the two equations,

5x = 20

x = 4

3(4) - y = 5

y = 12 - 5

y = 7

x² + 2yx

(4)² + 2(4)(7)

16 + 56

72

Answer 2

72

Explanation:

3x-y=5 and 2x+y= 15

Add the two equations together to eliminate y

3x-y=5

2x+y= 15

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

5x = 20

Divide by 5

5x/5 = 20/5

x = 4

Now we can find y

2x+y = 15

2(4) +y = 15

8+y =15

Subtract 8 from each side

8+y-8 = 15-8

y =7

We want to find

x^2+2xy

(4)^2 +2(4)(7)

16+56

72