Question

Solve the system using elimination.

–10x – 3y = –18
–7x – 8y = 11

A) (–4, 3)


B) (3, –4)


C) (2, –1)


D) (–7, –10)

Answer 1

We can't eliminate as is so we have to change something up there in the equations to get either the x values the same number but opposite signs, or the y values the same number but opposite signs. I chose to change the y values to the same number but different signs. In the first equation y is -3y and in the second one, y is -8y. The LCM of both of those numbers is 24, so we will multiply the first equation by an 8 (8*3=24) and the second equation by 3 (3*8=24) but since they are both negative right now, one of those multiplications has to involve a negative because - * - = +. Set it up like this:
8(-10x - 3y = -18)
-3(-7x - 8y = 11)
Multiply both of those all the way through to get new equations:
-80x - 24y = -144
21x +24y = -33
Now the y's cancel each other out leaving only the x's:
-59x = -177 and x = 3. Now plug that 3 into either one of the original equations to find the y value. Either equation will work; you'll get the same answer using either one. Promise. -7(3) - 8y = 11 gives a y value of -4. so your solution is (3, -4) or B above.

Answer 2

Answer:(3,-4)

Explanation:

Given equations are

-10x-3y=-18---------------1

-7x-8y=11-------------------2

From 1

18-3y=10x

x=1.8-0.3y

substitute the value of x in equation 2

`-7\left ( 1.8-0.3y\right )-8y=11`

-5.9y=23.6

y=-4

thus x=1.8+1.2

x=3

Thus (x,y)=(3,-4)