Question

Solve the system of linear equation. Hence find the value of p in 2x-5y = p, 4x-7y+28 = 0, 5y-7x+9 = 0.

Answer 1

2x - 5y  = P---(1)

4x  - 7y = -28---(2)

-7x + 5y = -9---(3)

From (2), 28x - 49y = -196---(4)

From (3), -28x + 20y = -36---(5)

on adding, we get -29 y = 232

⇒ y = 232/-29 = -8

\(\therefore\) x = \(\frac{-28+7y}{4}=\frac{-28-56}4=-7-14=-21\)

 \(\therefore\) P = 2(-21) - 5(-8) = -42 + 40 = -2