I would use substitution. For instance, the first:
y= x^2+4x
2x- (x^2+4x)=1
x^2-2x+1=0
(x-1)(x-1)=0
x=1 y=5
How do you solve these equations algebraically?
y=x^2+4x
2x-y=1
y=x^2+2x+3
x+y=1
1 answer
y=x^2+4x
2x-y=1
y=x^2+2x+3
x+y=1
1 answer