<s>[INST] Express the given polar equation in simplest rectangular form: $r = 4 + 3cosθ$ Express the given polar equation in simplest rectangular form: $r = 4 + 3cosθ$
My attempt
Multiplying r on both sides, we get
$r^2=4r+3 rcos\theta$
since, $x=rcos\theta$ and $y=rsin\theta$
and $r^2=x^2+y^2$
we get $x^2+y^2=4r+3x$
can anyone please explain after this step.. 
 [/INST] You have $r= 4+3\cos(\theta)$
$r^2 = 4r+3r\cos(\theta)$
we know that ;$x= r\cos(\theta)\qquad y = r\sin(\theta)$
$r^2 = x^2+y^2$
$\implies x^2+y^2 =\sqrt{x^2+y^2}+3x$
$\implies (x^2+y^2-3x)^2 = x^2+y^2$ 
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