I do not understand substitution

Question

Like described in image, I do not know how P1 become like that. Especially about why p1 is removed. Is there any formula used for this question?

$x=A+Bx\implies x=\frac A{1-B}$ – lulu Feb 25 '18 at 20:12 — lulu, Feb 25 '18 at 20:12
Not really substitution. More like algebra solving $P_1$ – Feb 25 '18 at 20:13 — , Feb 25 '18 at 20:13
Include the question as text, not as an image, please. – EJoshuaS - Stand with Ukraine Feb 25 '18 at 20:21 — EJoshuaS - Stand with Ukraine, Feb 25 '18 at 20:21

score 0 · Accepted Answer · answered Feb 25 '18 at 20:14

0

The equation is of the form

$$P_1=a+bP_1$$ which you rewrite

$$(1-b)P_1=a,$$ $$P_1=\frac a{1-b}.$$

answered Feb 25 '18 at 20:14

1 Answers1