Question

solve by substitution method
2x + 3y = 4, 3x - y = -5​

Answer 1

Answer:

$\huge \pink{x = - 1 \: and \: y = 2}$

Step-by-step explanation:

By second equation

$3x - y = - 5 \\ y = 3x + 5$

Substitute value of y in first equation

$2x + 3y = 4 \\ \\ \implies2x + 3(3x + 5) = 4 \\ \\ \implies2x + 9x + 15 = 4 \\ \\ \implies11x = 4 - 15 = - 11 \\ \\ \implies x = \frac{ - 11}{11} = - 1$

And

$y = 3x + 5 = 3( - 1) + 5 \\ \implies \: y = 5 - 3 = 2$

Answer 2

Answer:

x = -1

y = 2

Step-by-step explanation:

The second equation says,

3x - y = -5

or, y = 3x + 5

Let's substitute the value of y we got from the second equation, in the first equation.

2x + 3y = 4

or, 2x + 3(3x + 5) = 4 [substituting value of y = 3x + 5]

or, 2x + 9x + 15 = 4

or, 11x = -11

or, x = -1

Now let's find the value of y.

3x - y = -5

or, -3 - y = -5 [substituting value of x= -1]

or, y = -3 + 5

or, y = 2

Therefore x= -1 and y= 2.

Now just for verification, why did I choose the second equation to get the value of y and not the first? Because it was simpler to solve the value of y in that equation and substitute it, compared to the other equation. It all depends on the more convenient method.

Also, if you want, you can find the value of x and substitute it as well. The answer will be same.

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