Question

y = 4x + 6
y = -5x - 21
how to solve using substitution

Answer 1

Answer:

y = 4x + 6       (1)

y = -5x - 21    (2)

putting the value of (1) in (2):

4x + 6 = -5x -21

9x = -27

x = -3              (3)

putting the value of (3) in (1)

y = 4(-3) + 6

y = -6

Therefore x = -3 & y = -6

Answer 2

$\huge { \underline{ \underline{ \bold{answer}}}}→$

• x = -3
• y = -6

${ \underline{ \underline{ \bold{solution}}}}→$

we have,

• y = 4x + 6 .......(i)
• y = -5x - 21 .......(ii)

now, substitute the value of y from eq.(i) in eq.(ii)

$\bold{\implies y = - 5x - 21 } \\ \\ \bold{ \implies 4x + 6 = - 5x - 21 } \\ \\ \bold{ \implies 4x + 5x = - 21 - 6} \\ \\ \bold{ \implies 9x = - 27} \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \\ \\ \bold{ \implies x = \cancel{\frac{ - 27}{9} }} \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \\ \\ \bold{ \implies} \boxed { \bold{ \: x = - 3}}.......(iii) \: \: \: \: \:$

now, substitute the value of x from eq.(iii) in eq.(i)

$\bold{ \implies \: y = 4x + 6} \: \: \: \: \: \: \: \: \: \: \: \: \\ \\ \bold {\implies {y = 4 \times ( - 3) + 6}} \: \\ \\ \bold{ \implies y = - 12 + 6} \: \: \: \: \: \: \: \: \: \: \\ \\ \bold{ \implies}\boxed{ \bold{ y = - 6}} \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \:$

therefore, value of

• x is -3
• y is -6