#### Answer

no solution

#### Work Step by Step

Use the substitution method and solve the second equation for x
$x+y=4$
$x=4-y$
So substitute x to the first equation
$(4-y)^2+y^2=1$
$16-8y+y^2=1$
$y^2-8y+15=0$
By the quadratic formula, where a=0, b=-8, and c=15, we have
$y=\frac{8+/-\sqrt (-8)^2-2\times0\times15}{2\times0}$
Since denominator is 0, there is no solution