If (a, 2) is a point on the graph of y = 5x + 10 , what is a?

Question

Please help me

Answer 1

 
 
More detail of the problem statement:  When the line with equation (y=5x+10) is graphed, it crosses the point (a,2) [which is in (x,y) form, remember?].  That means that x=a and y=5 on the plot (graph).
 
The variables x and y are used to represent any point on those axes.  Constants like 2 and 10 represent known numerical values.  Letters like "a" are constants (not variables) with a singe unknown value.
 
This problem asks you to find the value of the constant "a" for which the point (a,2) is on the line (y=5x+10).
 
For both of these conditions to be true, we must have:
            2 = 5(a) + 10                    [insert x=a and y=2]
 
Now, we can use the rules of algebra to isolate "a" and determine its value.
 
Solution:
       2 = 5a + 10       [re-write]
      -8 = 5a             [subtract 10 from both sides because 10 had been added]
      -8/5 = a         [divide both sides by 5

                     because "a" had been multiplied by 5]
 
The value of a is (-8/5).
 
Checking (very important):
   Is point (-8/5,2) on the line (y=5x+10)   ?
         2 = 5(-8/5) + 10   ?
         2 = -8 + 10   ?
         2 = 2   ?yes

Answer 2

y = 5x+10  and the point (a,2) is on the line.

 

The question is:  What is the x value when y=2

 

2 = 5x + 10   Subtract 10 from both sides

-8 = 5x          Divide both sides by 5

-8/5 = x

 

Your point is (-8/5, 2)  and  a=-8/5