可唔可以教我計(5P+Q)x-4=Px+Q

(5P+Q)x-4=Px+Q
by comparing coeft of constant
Q=-4
by comparing coeft of x
5P+Q=P
5P+(-4)=P
4P=4
P=1//

(5P+Q)x-4=Px+Q

so, (5P+Q)x=Px, -4=Q

5P+Q=P , Q=-4

5P+(-4)=P

4P+(-4)=0

4P-4=0

4P=4

P=1

the answer is: P=1, Q=-4

(5P+Q)x-4=Px+Q，FIND P同Q

(5P+Q)x-4=Px+Q

5Px+xQ-4=Px+Q

4Px+xQ-4=Q

4Px+xQ-4-Q=0

4Px +Qx -(4+Q) = 0

4Px +Qx=4+Q

x(4P+Q)=4+Q

x = (4+Q)/(4P+Q)

比較2邊的係數
(5P + Q)x - 4 = Px + Q

5P + Q = P
Q = -4

5P + (-4) = P
4P = 4
P = 1

三個未知數要有三條式一得一條解唔到。
5Px + Qx -4 = Px +Q
4Px +Qx -(4+Q) = 0
x = (4+Q)/(4P+Q)