Question

solve the system of equations using substitution
y=3x-1
5x+2y=9
a.(1,2)
b.(3,1)
c.(2,1)
d.(1,3)

Answer 1

Substitution means that you would replace a variable used in one equation by the definition in another.
Example here: y=3x-1 defines (explicitly) what y is.
We can substitute y by 3x-1 in the second equation to get:
5x+2(3x-1)=9
which is one equation in one unknown.
From here, we can solve for x, and subsequently for y.

Answer 2

the simple explanation LOL.
When a question asks you to use substitution.. we can see from the first line that they ALREADY give you what "y" equals to (in this case y=3x-1)
So in the second equation it says 5x+2y = 9
And since we know that y=3x-1 , we would substitute the value of y into the second equation.
5x+ 2(3x-1) =9
Then we expand.
5x + 6x-2 = 9
Collect like terms and solve for x.
11x - 2 = 9
11x= 11
x= 1
Then since we know what "x" equals to, we substitute that value into y=3x-1
Sooooo,
y=3(1) -1
y=3-1
y=2.
So your answer is (1,2) and thus "a"

Answer 3

thanks

Answer 4

you are welcome :)