Question

The joint equation of the straight lines $x+y=1$ and $x-y=4$, is

• A. $x^2-y^2=-4$
• B. $x^2-y^2=4$
• C. $\left(x+y-1\right)\left(x-y-4\right)$
• D. $\left(x+y+1\right)\left(x-y+4\right)$

Answer 1

The correct option is C

$\left(x+y-1\right)\left(x-y-4\right)$

Explanation for correct option

Given: Equations of straight lines are $x+y=1$ and $x-y=4$.

Joint equations of straight lines are obtained by multiplying two equations:

so, a joint equation of straight lines $x+y=1$and $x-y=4$$=(x+y-1)(x-y-4)$

Hence Option C is correct i.e. $\left(x+y-1\right)\left(x-y-4\right)$