数学成长资源(Mathematical growth resources)

数学成长资源（Mathematical growth resources）

26.2 see a quadratic equation with the view of a function

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1. A

2. B

3. D

4. A

5. D

6. C

7.6 8. Minus 2 is less than or equal to 1

(1) y = (x - 1) 2-1 (2) - 1 or 3

(3) less than 0 or greater than 2 is greater than 0 and less than 2

10. Solution: y = x2-2x - 1 = x2-2x + 1-1-1 = (x-1) 2-2,

∴ vertex coordinates of (1, 2).

So y is equal to 0, x2 minus 2x minus 1 is equal to 0.

X1 is equal to 1 plus 2, x2 is equal to 1 minus 2.

∴ and intersection of the x a xis for the (1 + 2, 0), (1-2, 0).

(1) substitute (0, 3) into y = -x2 + (m - 1), and m = 4.

(2) minus x2 plus 3 is equal to 0, so x is equal to plus or minus 3,

∴ and intersection of the x axis (3, 0), (3, 0), the vertex coordinates of (0, 3).

(3) -3 < x < 3, the parabola is above the X-axis.

(4) when x > 0, the value of y decreases with the increase of x value.

The solution: (1) x2-2x - 3 = 0, x1 = -1, x2 = 3.

∴ A (1, 0), B (3, 0).

So if you plug in the coordinates of A, B, and B, and then you plug in y = ax2 + bx + 2,

So you get a minus b plus 2 is equal to 0, 9, a plus 3b plus 2 is equal to 0.

(2) it has to be (1) y = -23x2 + 43x + 2.

∵ when x = 0, y = 2, ∴ C (0, 2).

Let's say that the analytic formula for line AC is y is equal to k x plus b, and I'm going to put the two coordinates of A and C at y is equal to kx plus b, so k is equal to 2, and b is equal to 2.

∴ analytical type of linear AC y = 2 x + 2.

Similarly, the analytical formula for the line BC can be obtained

Y is equal to minus 23x plus 2.

Direct tests

1. C

2. D

3. X = -1,

4.12.5

5.4

(1) if you want to make a point, you can get 22 + 2p + + 1 = 0.

So q is equal to minus 2p plus 5.

(2) to prove: a yuan quadratic equation ∵ x2 + p + q = 0 discriminant Δ = p2-4 q,

By (1)

Δ = p2 + 4 (2 p + 5) = p + 20 p2 + 8 = (2 + 4 p + 4) > 0,

∴ a yuan quadratic equation x2 + p + q = 0, there are two not equal to the real root.

∴ parabolic y = x2 + p + q has two intersections with the x axis.

7. Solution: (1) drawing as shown.

Depends on the question

Y is equal to x minus 1, 2 minus 2 is x2 minus 2x plus 1 minus 2 is x2 minus 2x minus 1.

∴ translation after image analytic expression for y = x2-2-1 x.

(2) when y is 0, x2 minus 2x minus 1 is 0,

(x - 1) 2 = 2,

X minus 1 is equal to plus or minus 2,

X1 is equal to 1 minus 2, x2 is equal to 1 plus 2.

∴ the translation image and x axis to two points, coordinates, respectively (1-2, 0) and (1 + 2, 0).

It can be seen from the diagram that when x < 1-2 or x > 1 + 2, the quadratic function y = (x - 1) 2-2 is greater than 0.

26.3 practical problems and quadratic functions

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1. D

2. D

3. Y = -30x + 960 w = -30x2 + 960x - 1440

4. S = 2x2

5. Solution: (1) the profit of each loaf is (x-5) Angle, and the number of bread sold is (300-20x) or [160 - (x-7) x 20].