{x-4y =3 x^2-21y=28

Question

{x-4y =3 x^2-21y=28

Answer 1

x-4y=3 

x^2-21y=28

 

-4y=3-x

4y=x-3

y=1/4x-3/4

 

x^2-21*(1/4x-3/4)=28

x^2-5,25x+15.75-28=0

x^2-5,25x-12.25=0

D=27,5625+49=76,5625

SqrtD=8,75

x1=(5,25+8,75)/2=7

x2=(5,25-8,75)/2=-1,75

 

y=1/4x-3/4

y1=1/4*7-3/4=1

y2=1/4*(-1,75)-3/4=-1,1875