Bài giảng Song ngữ Đại số 9 - Period 19: Review and supplement the concepts of functions

Nội dung text: Bài giảng Song ngữ Đại số 9 - Period 19: Review and supplement the concepts of functions

1. teacher: tran quoc si
2. Function: hàm số. concept / ˈkọnˌsept /: khỏi niệm Formula /ˈfụrmyələ/ : cụng thức quantity ˈ/kwọntətē/ : đại lượng according / əˈkụrdiNG /: thay đổi corresponding /kọr-,ˌkụrəˈspọndiNG/ : tương ứng variable / ve(ə)rēəbəl / : biến số Explain : giải thớch defined : xỏc định evaluate / iˈvalyo͞ oˌāt /: tớnh, đỏnh giỏ Constant : hằng số graphs : đồ thị increasing : tăng, đồng biến decreasing : giảm, nghịch biến Skecth / skeCH /: vẽ, phỏc hoạ
3. Chapter I – LINEAR FUNCTIONS Period 19: Review andWhen thesupplement quantity y the concepts ofis calledfunctions the function of the change 1- The concept of function.quantity x? • y is called a function of x if: - A quantity y varies according to a changing quantity x. - Each value of x, we always identify only one corresponding value of y. When, y is called function and x is called variable.
4. Period 19: Review and supplement the concepts of functions Example 1 a. y is the * A function can be defined in a valuenumber table sand of x givenformula, by the table. Explain why y Ex1 : y is a function of x given by the following table: How many waysis a function of x ? to have function? x 1 1 1 2 3 4 3 2 y 6 4 2 1 1 2 2 3 Ex 3: y are function of x given by the following formula 4 b ) y = 2x; y = 3x+1; y = ; y = 1- x x
5. Period 19: Review and supplement the concepts of functions 1- The concept of function. * When a function is given by the formula y = f(x), that the variable x only get the value wich make f(x) defined * The function: y= 3x+1 and y= 2x Defined with x R 4 * The function y = Defined with x 0 x * The function y = 1− x Defined with x 1 * f(0); f(1); ; f(a) is value of function y= f(x) at x=0; x= 1; ; x=a.
6. Period 19: Review and supplement the concepts of functions 1- The concept of function. 1 Ex: The function y = f ( x ) = x + 5 evaluate: f(0)= 5 2 11 f(1)= 2 f(2)= 6 13 f(3)= 2 f(-2)= 4 f(-10)= 0 * When x change, if a function y always gets an unchanged value then y is called “ Constant function”.
7. Period 19: Review and supplement the concepts of functions 2- The graphs of functions: y ?2: a- Plot the fllowing points on the coordinate plane Oxy 6 A( ;6) A(1/3; 6); B(1/2; 4); C(1; 2); D(2;1); E(3; 2/3); F(4; 1/2) 4 B( ; 4) The set of points A, B, C, D, E, F on the 2 C(1; 2) coordinate plane are D(2; 1) 2 the corresponding 1 E(3; ) value pairs given by 2/3 3 F(4; ) the table ? 1/2 0 1 1 1 2 3 4 x 3 2
8. Period 19: Review and supplement the concepts of functions 2- The graphs of functions: y b- Sketch the graph of function y= 2x y= 2x Given x =1 y= 2 point 2 E A (1; 2) The graph of function y= 2 x 0 1 x * The set of all points which represent the pairs of corresponding value (x; f(x)) on the coordinate plane is called the graph of function y=f(x)
9. Period 19: Review and supplement the concepts of functions 3- Increeasing or decreasing functions: ?3: Evaluate the values of functions y=2x+1 and y = -2x+1 according to the corresponding values of variable x and fill in the following table x -2,5 -2 -1,5 -1 -0,5 0 0,5 1 1,5 y=2x+1 -4 -3 -2 -1 0 1 2 3 4 y=-2x+1 6 5 4 3 2 1 0 -1 -2 + The function y= 2x+1 defined by x R. The value of x is increasing, the corresponding value of y is also increasing => the function is increasing R + The function y= -2x+1 defined by x R. The value of x is increasing, the corresponding value of y is decreasing => the function is decreasing R
10. Period 19: Review and supplement the concepts of functions 3- Increeasing or decreasing functions: * In general Given the function y=f(x) defined by all the values of x in R. a- When the values of x is increasing, if the corresponding value of f(x) is increasing then the function y= f(x) is called the increasing function in R (or only increasing function in brief) b- When the values of x is increasing, if the corresponding value of f(x) is decreasing then the function y= f(x) is called the decreasing function in R (or only decreasing function in brief) In other words: for any value x1; x2 in R: If x1 f (x2) then fuction y=f(x) is is increasing in R
11. Period 19: Review and supplement the concepts of functions 4- PRACTICE 1 Sentence 2:book- 45: Given function y = - x + 3 2 Calculate the corresponding values of y according to the values of x then fill in the table below: x -2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5 y 4.25 4 3.75 3.5 3.25 3 2.75 2.5 2.25 2 1.75 a- The function is decreasing. Because the values x increasing but the values y decreasing. Sentence 3: Book- 45: a- Skecth the two given functions is in a same coordinate plane ? b- Among the given functions, which one is increasing ? Which one is decreasing ? Explain why ?
12. Period 19: Review and supplement the concepts of functions Sentence 2: Choose ansewer true: 1 a- Given function f(x)= x + 6 when f(-3) equal: 3 A: 9 B: 3 C: 5 D: 4 1 b- Given function g(x)= − x + 2 when f(3) equal : 3 A: 1 B: 3 C: -1 D: 2 Sentence 3: The function y= f(x)= -7 +3x is function A: increasing. B: increasing, decreasing to both. C: decreasing. D: Both A, B, C is false.
13. Period 19: Review and supplement the concepts of functions * HOME WORKS Sentence 1: Given function f(x) = ax4 – bx2 + x +3 (a, b is constant). Given f(2)= 17. Evalute f(-2) Sentence 2: Prove the graph of function y = f(x) = 33−xx + − is a point.