Middle school math questions. It s about systems of equations ... 20

<> see for yourself, the landlord has to work hard.

1):x=-3,y=6;(2),x=-5,y=3/2;x=1,y=;x=-2,y=5/9;(3) Let the first and second yields of the species be x kilograms and y kilograms respectively, and the system of equations according to the meaning of the problem is obtained, x+y=470, and the solution is obtained, x=250, y=220; Now the output of the first and second blocks is 290 and 242 respectively; A:,

1. y=-3，x=6

2.（1）x=-5,y=3/2

2）x=1，y=

3）x=-2，y=5/9

3.Let the two soils be x and y respectively, then there is the equation x+y=470, that is, x=470-y1+16%)x+(1+10%)y=523

470-y）*

y=370，x=100

16%x=16 10%y=37

1.Substituting x= into y=-3, y=0, x=62, use addition, subtraction and elimination.

1) x=-5, y=3 2(2)x=1,y=,x=-23 column equations. x+y=470,,y=370,x=100

It's not so simple, and it's not interesting to make it for you.

You have to study hard, don't just try to save energy.

This is my advice.

It's better to work your own.

1. Equation 1 multiplies m, and by adding equation 2, we can find x=2 (because m squared + 1 is not equal to 0, m=2 is true).

A similar method can be found with y=1

2. Let the velocities of A and B be x km h and y km h respectively by known listable equations.

2x+2x+2y=28

It can be solved with x=6 and y=2

3. m=9 (I don't want to write about the process).

4. "Together" means that the coefficient of one unknown in two equations is equal, and then subtracted to get the value of another unknown.

1.Make both formulas y=... and then solve x, and then substitute to solve the system of equations:,2x+2(x+y)=28.Just solve the system of equations.

There are countless solutions.

4.Substituting the value into the original equation, the equation is the solution.

5.These two formulas are listed together, and the solution must satisfy both formulas.

｛mx+y=2m+1①→m(x-2)=1-y③

x-my=2-m②→m(1-y)=2-x④

Bring in (m 2+1) (1-y) = 0

Because m 2 + 1 0, the case of m 2 + 1 0 is discarded. Therefore y=1

Bring y=1 to get x 2.

So {x 2

y=1, by drawing, it can be seen that in the same distance, the time ratio of A and B is 1, 2:3, 2, that is, 1:3, the velocity ratio is 3:1

Let A be 3xkm h and B be xkm h

So 4x 8

x=23x＝6

A:,The velocity of A is 6 km h, and the speed of B is 2 km h

This system of binary linear equations has an infinite number of solutions, meaning that it is a binary linear equation, i.e., 2x-3y+1=0 is the same as 6x-my+3=0.

So *3 , m=9

Substituting this pair of values into two formulas of a binary system of linear equations, the pair of values is the solution of the binary system of equations only when both formulas are true.

I understand that "together" means that binary equations complement each other, complement each other, and draw conclusions. The unknowns in the equation satisfy both binary equations.

1. Solution: (2) multiply m by m to get mx-m y=2m-m (3) (1) + (3) to get (1+m ) y=1+m y=1 (1) multiply m by m to get m x+my=2m +m (4) (4) + (2) (1+m )x=2(1+m) x=22, solution: let the speed of A be x kilometers per hour, and the speed of B be y kilometers per hour, that is, 4x+2y=28

The solution is x=6 y=2

3. Solution: (1) Equation is expanded 3 times to obtain 6x-9y+3=0 (2) equation is 6x-my+3=0

Observe 9y=my i.e. m=94, test the solution: substitute the solution into the equation to see if the left and right sides of the equation are equal, and then they can be combined: it is to put two equations with the same unknown number (or two related equations) together

Solution: Make the electricity cost of ordinary bulbs c1,c1=;

The cost of energy-saving bulbs is C2, C2=4+

To see that energy-saving bulbs save money over ordinary bulbs, require, c2-c1 0;

i.e.: 4+; Solution: H.

So it takes at least 602 hours to see that energy-saving lamps save money compared to ordinary lights.

It takes x hours for an energy-saving bulb to prove that it saves money over a regular bulb, 4+

It takes at least 602 hours to solve x.

ok。。

If there is such a problem in the future, it should be remembered that the question of how one thing is better than the other is to connect the two functions with an equal sign. Solve unary linear equations.

Solution: It takes at least x hours to set up an energy-saving light bulb to prove that it saves money compared to ordinary light bulbs, which is 4+ from the title

Solution x i.e. at least 602 hours to prove that it is cheaper than a regular light bulb.

Solution: Let the first method have an annual interest rate of x, and the second method has an annual interest rate of y.

Column equation 1000*x+20000y= <1>x+y= <2>

Solve the system of equations: x=y=

Let's say that the two interest rates are x and y respectively

Then: x+y=

1000x+20000y=

Simultaneous solution x,y is it!

｛2m+9n=

3m-5n=-15②｝

3: 6m+27n=

2: 6m-10n=30

Got: 37n=

n = -78/185

Bring in n = -78/185 to get: m = 195 out of 37 {m = 195 out of 37. }

n = -78/185

2m+9n=

3m-5n=15

6m+27n=

6m-10n=30

Then you can count it yourself, and despise it.

2m+9n=

If the left and right sides are divided by 2 at the same time, then m+9 2n= then m= is the formula 1. Substituting 1 into 3m-5n=-15, so 3( Simplifying n=222 185 m is your own three.

It's the second half of the semester, I haven't studied.

1.Untie; Because x+2z=3, so x=3--2z, because 2y+z=7, so y=(7-z) 2

Because 2x+y=2*(3--z)+(7--z) 2=2 gives z=5 3.Generations x=--1 3y=8 3A; x is --1 3

y is 8 3 z is 5 32. Untie; x/2=y/3=z/5 x/2=y/3 x=2y/3y/3=z/5 z=5y/3

So 2x+y+3z=2*2y3+y+3*5y3=88 solves the equation to get y=12, then x=2*12 3=8 z=5*12 3=20

A:,x is 8y is 12z is 20

1) The addition of the three formulas gives 3(x+y+z)=12, that is, x+ y+z=4 minus 1) to get y-z=1, and 3) the simultaneous solution gives y=8 3 z=5/3; x=-1/3.2), you may want to set x 2=y 3=z 5=k, then x=2k; y=3k;z=5k so 2x+y+3z=22k=88, so k=4; x=8;;;y=12 z=20.

3/3 x + 4/4 y=1

4/4 x + 3/3 y = 1

If it is sorted out to 4x+3y=12

3x+4y=12

Solution: x-y=0 x=y

Then bring this x=y in.

x 3 + y 4 = 1 x = y x 3 + x 4 x = 1x = 12 out of 7

y = 12/7

4x+3y=12

3x+4y=12

Then add the two equations together: 7x+7y=24 x+y=7 12 and then it's just a matter of how to do it.

。。。The top one subtracts the bottom one and this should get x-y=0 right... This problem can't be solved in this way, you use the most primitive method to solve it, from x 3 + x 4 = 1 to get x = (12-3y) 4, and then bring it in to calculate, the result is x = y = 12 7

Your method is correct, but it is wrong, and the answer is x=y=12 7

4x+3y=12

3x+4y=12

Add to get 7x+7y=24, x+y=24 7, subtract to get x-y=0, and add the two formulas to get 2x=24 7

The solution yields x=12 7 and y=12 7

Answer: Yes.

4x＋3y=12

3x＋4y=12

Rule. Get: x y=24 7

Get: x y=0

Get: x=12 7

Get: y=12 7

The solution is wrong, 4x+3y=12, 3x+4y=12, and x-y=0Then get x=y=12 7, I hope it helps you

4x+3y=12 times 3, then 12x+9y=36

3x+4y=12 times 4, then 12x+16y=48 is subtracted, 7y=12, y=12 7

Substituting gives x = 12 7

x=5+y into the second equation: 10-y=15

y=-5y=-5 The first concession of the first base of the kick-in: x+5=5x=06x-3y+3k=0

15+3k=0

k=-5