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krek1111 [17]
2 years ago
7

How can you decide which variable to solve first when you are solving a linear system by substitution

Mathematics
1 answer:
pshichka [43]2 years ago
6 0
I think you need to solve for x first to make the equation easier or simple.
You might be interested in
Please explain with working!!! Find the set of values of x that satisfy the inequality 9x^2-15x<6
Oksi-84 [34.3K]

Answer:

-1/3

Step-by-step explanation:

When solving a quadratic inequality, first solve it normally like you would for a normal quadratic equation. We have:

9x^2-15x

Ignore the less than sign and replace it with an equal sign and solve the quadratic for its zeros:

9x^2-15x=6

Subtract 6 from both sides:

9x^2-15x-6=0

Divide everything by 3:

3x^2-5x-2=0

Factor. Find two numbers that equal (3)(-2)=-6 that add up to -5.

-6 and 1 works. Thus:

3x^2-6x+x-2=0\\3x(x-2)+1(x-2)=0\\(3x+1)(x-2)=0

Find the x using the Zero Product Property:

3x+1=0 \text{ or }x-2=0\\x=-1/3\text{ or }x=2

Now, we need to replace the equal signs with symbols again. To do so, we need to test which symbol to place. Let's do the first zero first.

So, the first zero is:

x=-1/3

Assume that the correct symbol is >. Thus,

x>-1/3

Now, pick any number that is greater than -1/3. I'll pick 0 since it's the easiest. Now, plug 0 back into the very original inequality. If it works, then the sign is correct, if it doesn't, then simply use the opposite one. Therefore:

9x^2-15x

0 is indeed less than six, so our first correct solution is:

x>-1/3

For the second one, do the same thing. We have:

x=2

Assume that the correct symbol is <. Thus:

x

Again, pick any number less than 2. I'm going to use 0. Plug 0 back into the original equation

9x^2-15x

Again, this is correct. Therefore, x<2 is also the correct inequality.

So together, we have:

x>-1/3 \text{ and } x

Together, we can write them as:

-1/3

(Note that we don't need to worry about the "or equal to" part since the original inequality didn't have it.)

6 0
3 years ago
A solution of the equation 3x + y = 15?
Tamiku [17]

Step-by-step explanation:

Since there is 2 unknown variable ,

so we need 2 equation to find their values.

8 0
1 year ago
James would like to learn how to make omelettes. He polls his family about the number of eggs they each use to make one. He gets
Dmitry_Shevchenko [17]

Answer:

2 eggs

Step-by-step explanation:

Mean is average, so add all the numbers together then divide by how many numbers there are.

3 + 3 + 2+ 3 + 1 + 2 + 1 + 1 = 16

16 ÷ 8 = 2

4 0
2 years ago
A farmer planted 2/5 of his forty acres in corn and another 3/10 of his land in wheat
Mariana [72]

Answer:

7/10

Step-by-step explanation:

8 0
3 years ago
A/3=−18 (a/3 is a fraction)
allsm [11]

Answer:

Hey there!

a/3=-18

a=-54

Let me know if this helps :)

6 0
3 years ago
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