Question

5. Given: 2q – r = p, r = q – s, p = q + 2r; Prove: s = 2r

Answer 1

2q -r= p -----(1)

r= q -s -----(2)

p= q +2r -----(3)

From (2):

r +s= q (+s on both sides)

s= q -r -----(4) (-r on both sides)

Substitute. (3) into (1):

2q -r= q +2r

2q -q= 2r +r

q= 3r -----(5)

Substitute (5) into (4):

s= 3r -r

s= 2r (proved)