Question

Maria wants to solve the following system using the elimination method: 4x + 9y = 59 x + y = 17 What number should the equation x + y = 17 be multiplied by to eliminate y? 4 −4 9 −9

Answer 1

`\left\{\begin{array}{ccc}4x+9y=59\\x+y=17&|multiply\ both\ sides\ by\ (-9)\end{array}\right\\\\\underline{+\left\{\begin{array}{ccc}4x+9y=59\\-9x-9y=-153\end{array}\right}\\.\ \ \ -5x=-94`

Answer 2

we will multiply equation x+y=17 by (-9)

Explanation:

Maria has two equations to solve by elimination method:

4x + 9y = 59 ---- (1)

x +y = 17 ----------(2)

To start with elimination method we will multiply equation (2) by (-9) first,

-9x - 9y = -153 -------(3)

Now we will add equation (1) to equation (3)

4x + 9y = 59

-9x - 9y = -153

-5x = -94

5x = 94

x = 94/5

By putting x = 94/5 in equation (2)

`(94)/(5)`+ y = 17

y = 17 -
`(94)/(5)` =
`(85-94)/(5)`

=
`((-9)/(5))`

Answer : we will multiply equation x+y=17 by (-9)