Question

2x+y=1,3x-4y=18 find the value by substitution or elimination method​

Answer 1

Step-by-step explanation:

2x+y=1. =>6x+3y=3

3x-4y=18. =>6x-8y=36

-------------------. (subtraction)

11y=-33

y=-3

substitute y=-3 in 2x+y=1. =>2x+(-3)=1

=>2x=4=>x=2

therefore. x=2 and y=-3

Answer 2

Answer :-

• x = 2

• y = - 3

Explanation :-

Given

Pair of Linear equations

• 2x + y = 1--eq(1)

• 3x - 4y = 18 --eq(2)

I. Substitution method :

Finding the value of y in terms of x from eq(1)

⇒ 2x + y = 1

⇒ y = 1 - 2x

Substitute y = 1 - 2x in eq(2)

⇒ 3x - 4y = 18

⇒ 3x - 4(1 - 2x) = 18

⇒ 3x - 4 + 8x = 18

⇒ 11x - 4 = 18

⇒ 11x = 18 + 4

⇒ 11x = 22

⇒ x = 22/11

⇒ x = 2

Substitue x = 2 in y = 1 - 2x

⇒ y = 1 - 2(2)

⇒ y = 1 - 4

⇒ y = - 3

II. Elimination method :

Observe the coefficiets of y

Coefficients of y in to equations : 1 and - 4

LCM of 1 and 4 : 4

Multiply eq(1) with 4

⇒ 8x + 4y = 4 --eq(3)

Adding eq(3) and eq(4)

⇒ 3x - 4y + 8x + 4y = 18 + 4

⇒ 11x = 22

⇒ x = 22/11

⇒ x = 2

Substitute x = 2 in eq(2)

⇒ 3x - 4y = 18

⇒ 3(2) - 4y = 18

⇒ 6 - 4y = 18

⇒ 6 - 18 = 4y

⇒ - 12 = 4y

⇒ - 12/4 = y

⇒ - 3 = y

⇒ y = - 3

∴ x = 2 and y = - 3