Question

Solve by Substitution method: x+y=4 and 3x +11y=4......I will mark as brainiest

Answer 1

In Substitution method : We need to solve an equation for either x or y and then substitute that value in the second equation to get an equation which is of only one variable.

First Equation : x + y = 4

$\longrightarrow$  x = 4 - y

Second Equation : 3x + 11y = 4

Substitute value of x in Second Equation

$\longrightarrow$  3(4 - y) + 11y = 4

$\longrightarrow$  3(4) - 3y + 11y = 4

$\longrightarrow$  12 + 8y = 4

$\longrightarrow$  8y = 4 - 12

$\longrightarrow$  8y = -8

$\longrightarrow$  y = -1

Substitute value of y in x = 4 - y

$\longrightarrow$  x = 4 - (-1)

$\longrightarrow$  x = 4 + 1

$\longrightarrow$  x = 5

$\mathbf{\therefore\;\;x = 5\;\;and\;\;y = -1}$

Answer 2

$\textbf{\underline{\underline{According\:to\:the\:Question}}}$  

x + y = 4

Solve it in such a way to get the value of x

x = 4 - y ............ (Equation 1)

Now Second ⇒ 3x + 11y = 4

Now here put the value of x which we get from Equation (1)

⇒ 3(4 - y) + 11y = 4

⇒ 3(4) - 3y + 11y = 4

⇒ 12 + 8y = 4

⇒ 8y = 4 - 12

⇒ 8y = -8

$\tt{\rightarrow y = \dfrac{-8}{8}}$    

⇒  y = -1

Now put the value of y in Equation (1) we get :-

⇒ x = 4 - (-1)

⇒ x = 4 + 1

⇒ x = 5

${\boxed{\bigstar{{x = 5\:and\:y=-1}}}}$