Question

If x + y -7 = 0 and 3x + y- 13 = 0, then what is 4x2 + y2 + 4 xy equal to?

Answer 1

x+y-7=0 .....(1)
3x+y-13=0 ....(2)
x+y= 7 ....(3)
3x+y= 13. ...(4)
3 multiplying in eq.(3) &1 multiplying in eq.(4) ,then eq.(4) subtracting from eq.(3)
and get y=4
now putting the value of y in eq.(1)
x+y-7=0
x+4-7=0
x=3
now, 4x2+y2+4xy
=4×9+16+48
=100

Answer 2

Hi ,

Here we are using substitution method:

x + y - 7 = 0

y = 7 - x ----( 1 )

3x + y - 13 = 0-----( 2 )

put ( 1 ) in equation ( 2 ) , we get

3x + 7 - x - 13 = 0

2x - 6 = 0

2x = 6

x = 6/2

x = 3

substitute x = 3 in equation ( 1 ) , we get

y = 7 - 3

y = 4

Therefore ,

x = 3 , y = 4

Now ,

value of 4x² + y² + 4xy

= 4 ( 3² ) + 4² + 4 × 3 × 4

= 36 + 16 + 48

= 100

I hope this helps you.

:)