Question

On solving the pair of following linear equations by substitution method 3x - y - 7 =0, 2x +5=-1, the values of x and y are?

Answer 1

Given equation

• 3x - y - 7 = 0
• 2x + 5y = -1

To find

Find the value of x and y

Solution

Solve these equation by substitution method

• 3x - y - 7 = 0

=> 3x - y = 7

=> y = 3x - 7

Substitute the value of y in equation 2x + 5y = -1

• 2x + 5y = -1

=> 2x + 5(3x - 7) = -1

=> 2x + 15x - 35 = -1

=> 17x - 35 = -1

=> 17x = 35 - 1

=> x = 34/17 = 2

Again substitute the value of x in equation 3x - y -7 = 0

=> 3x - y = 7

=> 3 × 2 - y = 7

=> 6 - y = 7

=> y = 6 -7 = -1

${\boxed{\bf{Value\:of\:x=2}}}$

${\boxed{\bf{Value\:of\:y=-1}}}$

Answer 2

Given :

On solving the pair of following linear equati

ons by substitution method 3x - y - 7 =0, 2x +5=-1

To find :

Find the value of x and y

Solution :

Solve these equation by substitution method

So given equations are

• 3x - y = 7 --(i)
• 2x + 5y = -1 ---(ii)

From (i)

=> 3x - y = 7

=> y = 3x - 7

Substitute the value of y in equation (ii)

=> 2x + 5y = -1

=> 2x + 5(3x - 7) = -1

=> 2x + 15x - 35 = -1

=> 17x = 35 - 1

=> 17x = 34

=> x = 34/17 = 2

Putting the value of x in equation (i)

=> 3x - y = 7

=> 3 × 2 - y = 7

=> 6 - y = 7

=> y = 6 - 7

=> y = -1

Verification :

Putting the value of x and y in both the equation

• 3x - y = 7

LHS

=> 3x - y

=> 3 × 2 - (-1)

=> 6 + 1

=> 7 = RHS verified

• 2x + 5y = - 1

LHS

=> 2x + 5y

=> 2 × 2 + 5 × (-1)

=> 4 -5

=> -1 = RHS verified

Hence, both the equation verified