Mathematics Grade 8 Volume 1 p27 question 10

Mathematics Grade 8 Volume 1 p27 question 10

Review question 11ad = a ′ D ′ is proved as follows: ∵ ABC ≌ △ a ′ B ′ C ', so AB = a ′ B ′ - B = ∠ B ′, BC = B ′ C ′ - BD = (1 / 2) BC, B ′ D ′ = (1 / 2) B ′ C ′ BD = B ′ D ′. In △ abd and △ a ′ B ′ D ′, ab = a ′ B ′, ∠ B = ∠ B ′, BD = B ′ D} △ abd ≌ △ a ′ B ′ D ′ (s)

6 8
It's from volume one

6. You can refer to the example on page 127
8.10 minutes
9. List two relations Y1 = 0.8x y2 = x (0 ＜ x ≤ 200), the solution is 600, that is, when the cost is 600 yuan, the two families are the same, when the cost is greater than 600, choose B, otherwise = 200 + 0.7x

Chapter 1 1.1 understanding triangles (2) all answers

1. C = 80 ° 2. D = e = 75 ° 3. ADC = 80 ° 3. 2 acute angles, 3 right angles, 1 obtuse angle, 4
∵∠ C = RT ∠, i.e. ∠ C = 90 °,
∠B=∠C/4
∴∠B=90°/4=22.5°
∴∠A=180°-∠B-∠C=180°-22.5°-90°
∠A=67.5°

Let f (x) = 2aX (square) - ax, f (x) = - 6, then a=

Does f (x) = - 6 leave out the condition and the domain of X?

3 out of 5 * 6 out of 5 = 1 out of 4 * 7 out of 2 = 5 out of 13 * 7 out of 4 * 14 = 4 out of 9 * 5 * 18

3 / 5 × 5 / 6, about 5 and 5, about 3 and 6
=1×1/2
=1/2
1 / 4 × 2 / 7 2 and 4 fractions
=1/2×1/7
=1/14
About 5 / 13 × 4 / 7 × 14 and 7
=5/13×4×2
=40/13
About 4 / 9 × 5 × 18 and 9
=4×5×2
=40

If and only if ()
A. a＞0B. a＜0C. -10＜a＜30D. -5＜a＜27

If f ′ (x) = 3x2-6x-9 = 3 (x-3) (x + 1), f ′ (x) ≥ 0, X ≥ 3 or X ≤ - 1; if f ′ (x) ＜ 0, f ′ (x) ＜ 1 ＜ x ＜ 3. The function increases monotonically at (- ∞, - 1], [3, + ∞), decreases monotonically at (- 1,3), and the function reaches the maximum at x = - 1, and takes the maximum at x = 3

How many different ways can you compare the size of 8 / 9 and 7 / 8?

1. Make a decimal
2. Sharing
3. Compare the size of 1 / 9 and 1 / 8, and introduce

What is the maximum value of the function y = 3sin (X-10) + 5sin (x + 50)?

Let X-10 ° = a
y=3sinA+5sin(A+60°)
=3sinA+5sinAcos60°+5cosAsin60°
=(11/2)sinA+(5√3/2)cosA
=√[(11/2)²+(5√3/2)²]sin(A+∅)
=√49sin(A+∅)
=7sin(A+∅)
The maximum value of sine is 1,
So, the maximum value of Y is 7

Simple algorithm: 1 / 8 × 7 / 11 + 4 / 11 △ 2 / 8 [9 / 14 × (5 / 5-4 / 9)]

1 / 8 * 11 / 7 + 11 / 4 △ 8 = 1 / 8 * 7 / 11 + 4 / 11 * 1 / 8 = 1 / 8 * (7 / 11 + 4 / 11) = 1 / 8 * 1 = 8 / 13 / 2 △ [9 / 14 × (5-9 / 4)] = 2 / 3 ^ [9 / 14 × (1-9 / 4)] = 2 / 3 ^ [9 / 14 × (9-9 / 4)] = 2 / 3 ^ [9 / 14 × (9-9 / 4)] = 2 / 3 ^ [9 / 14 × (9-9 / 9)]

Given the quadratic function y = - x ^ 2 + 4, when - 2 ≤ x ≤ 3, the minimum value is the maximum value

The solution is downward from the opening of the function image, and the axis of symmetry is x = 0
We know that when x = 0, y has a maximum of 4
When x = 3, y has a minimum value of y = - 5