Classroom Reflection V (from english lesson on April 25th, 2013 with Mr. Marsigit)

               On that day, Mr. Marsigit show us certain videos about mathematics and english. He just ordered us to make reflection just from the videos about mathematics. That are video about inverse function and quadratical form and from video about a student that give a speech entitled ‘Do You Believe in Me ?’



              First, i’ll talk about student speech video. In the video, there is  10 year old orator spoke in front of a crowd of teachers. The theme of his speech is “Do you believe in me?” He says that students can “do anything, create anything, dream anything and become anything” if they believe in themselves. He stresses that often students only come to believe in themselves when their teachers believe in them. He goes on to tell the audience that teachers must not give up on their student. Teachers must trust the student that they can do the best in the process of constructing their ability. This is very inspiring video, because from this video we can learn that a trust from the teacher is important for the student. And then as a student, we must keep the trust that given for us.

            The first mathematics video is about inverse function. The video told us about how to find the inverse of the function. First, We must know about what is a function, a function takes a starting value, performs some operation on this value, and creates an output answer.  And then, the inverse function takes the output answer, performs some operation on it, and arrives back at the original function's starting value. Basically speaking, the process of finding an inverse is simply the swapping of the x and y coordinates. And there is a difference of inverse of a function and inverse function. Inverse of a function may not be a function and inverse function is an inverse of function that itself a function.

            Now i’ll talk about how to find inverse function. Firstly, write the entire function out, replacing f(x) or g(x) with y. To use our example function, you'd rewrite f(x) = 5x - 2 as y = 5x - 2.  f(x) and y are interchangeable. f(x) is the standard function notation, but if you're dealing with multiple functions, each one gets a different letter to make telling them apart easier. For example, g(x) and h(x) are each common identifiers for functions. And then, solve for x, or in other words, perform the necessary mathematical operations to isolate "x" by itself on 1 side of the equal sign. Remember, you can perform any operation on 1 side of the equation, as long as you perform the operation on every term on both sides of the equal sign. To continue our example, you'd first add 2 to both sides of the equation. This gives us y + 2 = 5x. You'd then divide both sides of the equation by 5, yielding (y + 2)/5 = x. Finally, you'd rewrite the equation with "x" on the left side: x = (y + 2)/5. And then, switch the variables, replacing "x" with "y" and vice versa. The result is the inverse of the original function. To complete our example, you'd have y = (x + 2)/5. Finally, check your work by substituting a constant into the original function. For example, try substituting 4. This gives you f(x) = 5(4) - 2, or f(x) = 18. If you found the correct inverse, you should be able to plug the result--18--into the inverse function and get your original x-value as the result. 

           The second video is about quadratic form, this video told us that any equation 

in the form ax2 + bx+ c = 0 is said to be in quadratic form. This equation then can 

be solved by using the quadratic formula, by completing the square, or by factoring 

if it is factorable. Quadratic equations of type ax2+ bx + c = 0 and  ax2 + bx = 0 

(c is 0) can be factored to solve for x. After we factorize the equation, we can use 

the principle of zero products, which says, if pq = 0, either p, q, or both must be 

equal to zero. And then, the solutions of any quadratic equation, ax2 + bx + c = 0 

is given by the following formula, called the quadratic 

formula: 

 

    The way to get the soluion are firstly find the standard form of the equation and determine a, b,and c.

Then plug the values you found for a, b, and c into the quadratic formula, perform any indicated operations.Finally we can get the solution. 

       

           But the both video just present the material, not teaching, so that, we as a teacher must not imitate the method of teaching on that video.