need help with algebra 1 homework?

Question

solving linear systems by substitution


question



y=3x

y=2x-7

Answer 1

im going to label the problem into 1 and 2.

1.) y=3x
2.) y=2x-7

since Y equals something on both sides... plug in what Y equals to either equation. So it looks something like this:
3x=2x-7
1. Subtract : 3x-2x =1x
2. Now, the equation should look like this: 1x= -7
3. x= -7
4. Plug in x to either equation.
5. I'll do it like this: y= 3( -7 )
6. y= -21
7. Answer is... -7, -21

Answer 2

OK....in BOTH equations, we know what y is equal to. So let's take one of them (the first one) and "substitute" it into the other one....

This turns into 3x = 2x - 7. Now take and SUBTRACT 2x from BOTH sides, and you get 1x = -7, and we know that 1x is the same as just "x", so x = -7 !

Now that we know what x is, we can put it back in to EITHER of the equations, and solve for y. Let's use the first equation again...

y = 3x becomes y = 3(-7). This is y = -21 !

You can CHECK your answers in BOTH equations now to see if your are correct...

-21 = 3(-7) -21 = -21 YEP this one is good !

-21 = 2(-7) - 7 >>>>> -21 = -14 - 7 >>>>> -21 = -21 YEP, this one is good too ! Our answers are correct !

Good luck.

Answer 3

Tom's right, since you know what y is directly, if you put 3x into y=2x -7 and get 3x=2x -7, then you just subtract 2x from both sides and get x= -7

Answer 4

since y=3x and y=2x-7 you can substitute the y's
so you end up with:
3x=2x-7 subtract 2x from both sides and you get
-2x -2x
x=-7
then plug x in one of the equations to get y

y=3(-7)
y=-21

Answer 5

if y equals 3x, it should be substituted for the y in y=2x-7.:

y=3x
y=2x-7
now it would look like this if you put 3x in place of y:
3x=2x-7

subtract 2x from both sides:
x = -7

now you can solve:

y=3(-7)
y=2(-7) - 7
y=-21

and see if it checks both problems with x=-7 and y=-21

Answer 6

substitute the first value for y into the second equation

3x = 2x - 7

then solve for x by subtracting the 2x from both sides

3x - 2x = 2x - 2x - 7

3x - 2x = 0x - 7

3x - 2x = -7

x = -7

so that is your answer for x, x = - 7

then to find y, substitute - 7 for the value of x in the first equation

y = 3x

y = 3 (-7)

y = - 21

Answer 7

take the 2nd equation and isolate for x:
y=2x-7 becomes (y+7)/2 = x

then substitute that in the 1st equation:
y=[3(y+7)]/2

cross multiply and isolate the y.
2y = 3y + 21
-y=21
y=-21

take this y-value, and sub into the first equation:

y=3x
-21=3x
-7=x

im sure you couldve substituted the other way... but this is what i got.

Answer 8

A.) a finished of 456 tickets have been offered, so a + s = 456. the quantity of money made out of each and every style of value ticket is its value expanded by using what proportion have been offered. for this reason, the quantity of money made out of the person tickets on my own is $3.50 * a = 3.5a money. Likewise, the quantity of money made out of the pupil tickets on my own is $a million * s = s money. the excellent value ticket sales equals $1131, so 3.5a + s = 1131. subsequently, your gadget of equations is: a + s = 456 3.5a + s = 1131 B.) Multiply the 1st equation by using -a million so that's -a - s = -456. Now upload this equation to the 2d equation to clean up for a via removing s from the ensuing equation: (3.5a + s = 1131) + (-a - s = -456) = (2.5a = 675) 2.5a = 675 (divide the two factors by using 2.5) a = 270 And you may now clean up for s. a + s = 456 (replace 270 for a) 270 + s = 456 (subtract 270 from the two factors) s = 186 answer: 270 person tickets and 186 pupil tickets

Answer 9

Substitute the 3X into the second equation for Y and then solve for X.

Answer 10

ok so for y=3x, u would plot a point at (0,0) because u don't have a x-axis. and to get the slope u would go up 3 units and over 1 unit.

and for y=2x-7, u would plot ur point at (-7,0) and to get the slope u would go up 2 and over one. hope i could help.