Question

Solve the pair of equations by substitution method: 3x+4y= -6 and 3x-y= 9.​

Answer 1

Solution

Given That :-

• Equation, 3x + 4y = -6 --------(1)
• 3x - y = 9 ----------(2)

Find :-

• Value of x & y ,by substitution method

Explanation

Substitution Method

By, equation (2)

➡ y = 3x - 9 -----------(3)

Keep Value in equ(1)

➡ 3x + 4 * (3x - 9) = -6

➡ 3x + 12x - 36 = -6

➡ 15x = -6 + 36

➡ x = 30/15

➡ x = 2

Keep Value in equ(3)

➡ y = 3 * 2 - 9

➡ y = 6 - 9

➡ y = -3

Hence

• Value of x = 2
• Value of y = -3

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Answer 2

SOLUTION:-

Given

▪︎ 3x+4y=-6

▪︎ 3x-y=9

To find

Value of x and y

Explanation

Substitution Method !

▪︎ 3x+4y=-6____________(1)

▪︎ 3x-y=9_______________(2)

Taking eq 2

▪︎ 3x-y=9

= 3x=9+y

= x= 9+y / 3

Putting Value of x in eq 1

▪︎ 3x+4y=-6

= 3×(9+y / 3) +4y =-6

= 27+3y / 3 +4y=-6

= 27+3y+12y / 3 = -6

= 27+15y / 3 =-6

= 27+15y=-6×3

= 27+15y= -18

= 15y= -18-×7

= 15y = -45

= y= -3

Putting value of y in eq 2

▪︎ 3x-y=9

= 3x-(-3)=9

= 3x= 9-3

= 3x= 6

= x= 2

So the value of x=2 and y= -3.

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