Question #589e3

2 Answers
Ratnaker Mehta
Jul 6, 2016

Option (b) : x+y+1=0.

Explanation:

There are #2# Methods to deal with the Problem :-

Method I: Method of Verification :-

Given that the line passes thro. the pt. #(1,-2)#, its co-ords. must satisfy the eqn. of line. We see that eqn. (a) is not satisfied, but eqn (b) is satisfied.

Next we verify the #2^(nd)# cond. This cond. is satisfied by the eqns. of both the lines; for#(a)# equal intercepts are #1#, those for #(b), -1.#

Thus, #(b)# fulfils both the conds.

Hence, The Answer is Option (b) : x+y+1=0.

But, I should point out the Limitation of this Method (of Verification) :

Let us not forget that we have been able to verify the given conds. because the eqns. ,or, rather, options for the conds., were readily available. So, this Method will work only when we have options to choose from!

Method II :

In this Method , we try to derive the eqn. of a line satisfying the conds.

We use the Intercept Form of Line : In the Usual Notation , this is given by #: x/a+y/b=1.#

Given that #a=b#, we have, #x/a+y/a=1,#, or, #x+y=a# & since #(1,-2) in [x+y=a]#, we have, #1-2=a#, giving, #a=-1#, so the eqn. is, #x+y=-1#, i.e., #x+y+1=0#.

Hence, Option (b) : x+y+1=0., as before!

Was this helpful?, if yes, then enjoy Maths. as I Do!

Nallasivam V
Jul 6, 2016

The correct equation is #x+y+1=0#

Explanation:

To find which equation is the right one, Substitute the values in the equations.

#x+y=1#-----------------(1)
#1 + (-2)=1#
#1-2 !=1# This is not the equation.

#x+y+1=0#
#1-2+1=0# This is the equation.

Its x-intercept is #=-1#
Its Y-intercept is #= -1#

Look at the graph

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