It is known that the quadratic function f (x) = AX2 - (a + 2) x + 1, a is an integer, and the function f (x) has exactly a zero point on (- 2, - 1). An analytic trial of finding f (x)

It is known that the quadratic function f (x) = AX2 - (a + 2) x + 1, a is an integer, and the function f (x) has exactly a zero point on (- 2, - 1). An analytic trial of finding f (x)

The answer is as follows:
This should be a senior one mathematics compulsory equation zero problem, the basic point LZ should understand?
It is known that f (x) is a quadratic function, so a ≠ 0
Then there are two cases
① The zero point of F (x) on (- 2, - 1) is not the vertex of F (x) image
List the equations to restrict the conditions
If f (- 2) · f (- 1) < 0, then f (x) is restricted to have exactly one zero point on (- 2, - 1)
The solution is - 3 / 2

The function f (x) = AX2 - (a + 2) x + 1 is known. If a is an integer and f (x) has a zero point in (- 2, - 1), the value of a is obtained

(1) When a = 0, from F (x) = AX2 - (a + 2) x + 1 = - 2x + 1 = 0, we can get x = 12, so f (x) has no zero point in (- 2, - 1); (2) when a ≠ 0, from F (x) = AX2 - (a + 2) x + 1, △ = (a + 2) 2-4a = A2 + 4 > 0, we know that f (x) = AX2 - (a + 2) x + 1 must have two zeros

The average number of a, B and C is 70, a: B = 2:3, B: C = 4:5, B number______ ．

A: B = 2:3 = 8:12, B: C = 4:5 = 12:15, so a: B: C = 8:12:15, 8 + 12 + 15 = 35, 70 × 3 = 210, 210 × 1235 = 72, a: B is 72

If the equation (SiNx) ^ 2-2sinx + 3-m = 0 has a real solution, the range of real number m is

(SiNx) ^ 2-2sinx + 3-m = 0 has real solution
Then f (x) = x ^ 2-2x + 3-m = 0 has roots in [- 1,1]
The axis of symmetry of y = f (x) is x = 1,
Then f (- 1) × f (1)

One third of 90 is (), () two fifths is 20, 60 two thirds is 80 ()

Mathematical answer group for you to answer, I hope to help you
One third of 90 is 30, two fifths of 50 is 20, two thirds of 60 is 80

Given 2 ^ x = 3, 2 ^ y = 5, try to find the value of 2 ^ 3x + 2Y + 2

It is known that 2 ^ x = 3, 2 ^ y = 5
therefore
2^3x+2y+2
=2^3x·2^2y×2^2
=(2^x)³×(2^y)²×4
=3³×5²×4
=27×25×4
=2700

For a batch of parts, Party A does it alone for 20 days, and Party B does it alone for 30 days. Party A and Party B work together for several days. Party B asks for leave because of business, and Party A continues to finish the parts processing
How many days have you asked for leave?

16-（1-1/20×16）÷（1/30)=10

Solving equation 8x (5-x) = 19-2x (4x-3)

40x-8x^2=19-8x^2+6x
40x=19+6x
40x-6x=19
34x=19
x=19/34

Hongyuan electric appliance store has a color TV set. If it is sold at a price reduction of 10%, it will make a profit of 215 yuan. If it is sold at a price reduction of 20%, it will lose 125 yuan. So how much is the price of this color TV set?

Set the price as X Yuan (1-10%) x-215 = (1-20%) x + 125 & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; 0.1X = 340 & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; X = 3400 A: the price of this color TV is

0.7x + 0.3 = 8.8 the equation was wrong just now

0.7x+0.3=8.8
0.7x=8.8-0.3
0.7x=8.5
x=85/7