Question

3x-y=7 2x+4y=0 by the method of substitutions ​

Answer 1

Answer:

Given 3x – y = 7 … (1)

2x + 4y = 0 … (2)

Expressing y of equation (1) in terms of x,

⇒ 3x – y = 7

⇒ 3x - 7 = y … (3)

Substituting (3) in (2),

⇒ 2x + 4y = 0

⇒ 2x + 4 (3x – 7) = 0

⇒ 2x + 12x – 28 = 0

⇒ 14x – 28 = 0

⇒ 14x = 28

∴ x = 2

Substituting x value in (3),

⇒ 3x – 7 = y

⇒ 3 (2) – 7 = y

∴ y = -1

∴ By solving, we get x = 2 and y = -1.

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Answer 2

$\huge{\bf{\underline{\red{Solution :}}}}$

Given Equation :-

• 3x - y = 7
• 2x +4y = 0

According to the Question :-

∴Firstly Solve First Equation and Find Value of x .

$\implies \sf{3x - y = 7}$

$\implies \sf{3x =7 + y}$

$\implies \boxed{\sf{x = \dfrac{7 + y}{3}}} \ \ \sf{1)Equation}$

Now Put Value of x in Second Equation :-

$\implies \sf{2x + 4y = 0}$

$\implies \sf{2(\dfrac{7 + y}{3} ) + 4y = 0}$

$\implies \sf{\dfrac{14 + 2y }{3} + 4y = 0}$

$\implies \sf{\dfrac{14 + 2y + 12y}{3} = 0}$

$\implies \sf{\dfrac{14 + 14y }{3} = 0$

$\implies \sf{14 + 14y = 0}$

$\implies \sf{14y = - 14}$

$\implies \sf{y = \dfrac{-14}{14}}$

$\implies \boxed{\sf{y = -1}}$

Now Put the value of y in First Equation :-

$\implies \sf{x = \dfrac{7 + y}{3}}$

$\implies \sf{x = \dfrac{7 - 1}{3}}$

$\implies \sf{x = \dfrac{6}{3}}$

$\implies \boxed{\sf{x = 2}}$

$\rule{200}2$