How do you know (2,1) is a solution to 4x +y=9

4x+y=9

4(2)+(1)=9

8+1=9

9=9

It is a solution

9=9

Step-by-step explanation:

Solution:

x = 2

y = 1

4x+y=9

4(2) + (1)=9    (here 4 and 2 are multiplying with each other, so 4x2= 8)

8+1=9

9=9

not only in mathematics, scientific proof also are required in the other field of science. also maths proofs are of particular structure, containing steps and logics. so proving is like doing science, it is science. that's why it is important to prove. 

an inaccurate proof leads to errors, or stating results that are not accurate.  which wil mess the probelm up you dont want this

54 km / hours

step-by-step explanation:

we need to convert seconds to hours

60 seconds = 1 minutes

60 minutes = 1hour

15 m         60 second   60 minutes

  * *         = 54000 meters/ hour

second     1 minute             1 hour

now we need to convert meters to km

1000 m = 1 km

54000 m       1 km

*   = 54 km / hours

hour               1000m