How do you solve this system of equations using the substitution method $x - y = 1 and 4 x + 9 y = - 87$ $x- y = 1 and 4x + 9y = - 87$ ?

Question

How do you solve this system of equations using the substitution method $x - y = 1 and 4 x + 9 y = - 87$ $x- y = 1 and 4x + 9y = - 87$ ?

2 Answers

Impact of this question

2797 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2018-08-13T07:31:27

$y = - 7$ $y=-7$
$x = - 6$ $x=-6$

Explanation:

Given -

$x - y = 1$ $x-y=1$ ----------------(1)
$4 x + 9 y = - 87$ $4x+9y=-87$ ----------(2)
Solve equation (1) for $x$ $x$
$x = 1 + y$ $x=1+y$
Substitute $x = 1 + y$ $x=1+y$ in equation (2)
$4 (1 + y) + 9 y = - 87$ $4(1+y)+9y=-87$
$4 + 4 y + 9 y = - 87$ $4+4y+9y=-87$
$13 y = - 87 - 4 = - 91$ $13y=-87-4=-91$
$y = \frac{- 91}{13} = - 7$ $y=(-91)/13=-7$

$y = - 7$ $y=-7$

Substitute $y = - 7$ $y=-7$ in equation (1)

$x - (- 7) = 1$ $x-(-7)=1$
$x + 7 = 1$ $x+7=1$
$x = 1 - 7 = - 6$ $x=1-7=-6$

$x = - 6$ $x=-6$

Answer 2 · 2018-08-13T07:37:30

$x = - 6 and y = - 7$ $x=-6 and y=-7$

Explanation:

Here ,

$x-y=1 =>x=y+1.....to(1)$

$4x+9y=-87.................to(2)$

Substitute value of $x$ from $(1)$ into $(2)$

$4(y+1)+9y=-87$

$4y+4+9y=-87$

$13y=-91$

$:.color(red)(y=-7$

Subst. $color(red)(y=-7$ into (1)

$x=color(red)(-7)+1=>color(blue)(x=-6$

Hence , $x=-6 and y=-7$

Science

Math

Humanities

... and beyond

How do you solve this system of equations using the substitution method $x - y = 1 and 4 x + 9 y = - 87$ $x- y = 1 and 4x + 9y = - 87$ ?

2 Answers

Explanation:

Explanation:

Related questions

Impact of this question

Science

Math

Humanities

... and beyond

How do you solve this system of equations using the substitution method x- y = 1 and 4x + 9y = - 87x−y=1and4x+9y=−87x- y = 1 and 4x + 9y = - 87?

2 Answers

Explanation:

Explanation:

Related questions

Impact of this question

How do you solve this system of equations using the substitution method $x - y = 1 and 4 x + 9 y = - 87$ $x- y = 1 and 4x + 9y = - 87$ ?