Question

43. Ifa+b= -2 and a-b = 12,find b.
a) 5
b) -5
c) 7
d) -7​

Answer 1

Answer:

d) - 7 is the correct answer.

Step-by-step explanation:

Given:

a + b = - 2-----------------(Eq - 1)

a - b = 12----------------(Eq - 2)

The given are a pair on linear equations in two variables.

We can either solve it by elimination, substitution, graphically or Cross - Multiplication.

Elimination is the easiest method according to me as it takes very less time and not complicated also.

Solving by Elimination:

=> a + b = - 2

=> a - b  =  12                    (Adding Eq 1 and Eq 2)

=> 2a = 10

=> a = 10 / 2 = 5

= 5

Substituting value obtained for a in Eq 1:

5 + b = - 2

b = - 2 - 5

b = - 7

According to question we are asked to find the value of b and from what we found out value of b is - 7.

Therefore, Option d) - 7 is the correct answer.

Answer 2

Given ,

a + b = - 2 --------- (i)

a - b = 12 --------- (ii)

By using elimination method , add equation (ii) and eq (i) , we get

$\sf \implies (a - b) + (a + b) = 12 + (-2) \\ \\ \sf \implies </p><p>2a = 10 \\ \\ \sf \implies </p><p>a = 5$

Put the value of a = 5 in equation (i)

$\sf \implies 5 + b = -2 \\ \\\sf \implies </p><p>b = - 2 - 5 \\ \\ \sf \implies </p><p>b = -7$

Hence , the required value of b is -7