The two roots of equation x ^ 2-3x-1 = 0 are the roots of equation x ^ 4 + ax ^ 2 + BX + C = 0 (1) The value of a + b-2c; (2) 11A + 3B + 2C

The two roots of equation x ^ 2-3x-1 = 0 are the roots of equation x ^ 4 + ax ^ 2 + BX + C = 0 (1) The value of a + b-2c; (2) 11A + 3B + 2C

If X & # 178; - 3x-1 = 0x & # 178; = 3x + 1 (X & # 178;) = (3x + 1) &# 178; X ^ 4 = 9x & # 178; + 6x + 1x ^ 4-9x & # 178; - 6x-1 = 0, then: (1) a = - 9, B = - 6, C = - 1A + b-2c = - 9-6 + 2 = - 13 (2) 11a + 3B + 2C = - 99-18-2 = - 119

Junior high school equations to solve practical problems (bivariate quadratic equation) please explain the reasons for equations
When the sink leaks, it takes 2 hours for pipe a to open, 3 hours for pipe B to open, and 1 hour for pipe a and pipe B to open at the same time. When the sink does not leak, how long does it take for pipe a and pipe B to open and fill the sink at the same time?

Let a efficiency a / h, B efficiency B / h, leakage M / h, according to the meaning of the problem: 2a-2m = a + B + m, the solution is A-B = m; 3b-3m = a + B + m, the solution is - A + 2B = 2m; solving this equation system is a = 4m, B = 3M. Then the volume of the tank is expressed by m as 2 * 4m-2m = 6m

The solution of the equation a (x + m) square + B = 0 of X is X1 = - 2, X2 = 1 (a, m, B are all constants, a ≠ 0), then what is the solution of the equation a (x + m + 2) square + B = 0
Why do I set (x + m) to y ay & # 178; + B = 0? The equation a (x + m + 2) &# 178; + B = 0 becomes the equation a (y + 2) &# 178; + B = 0. After opening a (Y & # 178; + 4Y + 4) + B = 0, a Y & # 178; + B = 0 is brought into 4ya + 4A + B = 0, that is, 4a (x + m) + 4A + B = 0. So there should be only one solution? Why are there still two solutions

This is a quadratic equation of one variable. There are several roots to judge its discriminant. You should understand this. If you don't calculate its discriminant, you will eliminate its quadratic term, which will inevitably lose the root. Can you find the correct root by your algorithm? And if you want to find the root of the equation, you must first determine the value of a, B, M

The absolute value of X-1 + the absolute value of X-2 is added to the absolute value of x-1997, and the minimum value is a.0 b.998
C.999 D.1997

If the sum number is the minimum, obviously all four answers are wrong
If you want to find the minimum value of X, then the answer is 999, choose C
Suppose x = 0, that is 1 + 2 + 3 + +The sum of 1997
When x = 1998, it is 1997 + +The sum of 3 + 2 + 1, which is symmetric, exceeds the value of X between 0 and 1998
From the symmetry, when x should be in the middle of 1 ~ 1997, the dispersion is the lowest, and the middle value is (1997-1) / 2 + 1 = 999,
The minimum value of sum is 998 + 997 + +2+1+0+1+2+… +997+998=2*{（1+998）*998/2}=498501.

The image of function f (x) = LG [2 / (x + 1) - 1] is symmetric with respect to (?)?
1. X axis 2. Y axis 3. Origin 4. Straight line y = x,

F (x) = LG {(2 / x + 1) - 1} = LG [(2-x-1) / (x + 1)] = LG [(1-x) / (x + 1)] f (- x) = LG [(1 - (- x)) / (- x + 1)] = LG [(x + 1) / (1-x)] = LG [(1-x) / (1 + x)] ^ - 1 = - LG [(1-x) / (x + 1)] - f (- x) = LG [(1-x) / (x + 1)] so f (x) = - f (- x) so the function y = LG {(2 / x + 1) - 1} is odd and symmetric about the origin

Prime number: 21 = 2 + 19 = + = 3 × 7 8 = () + ()

21=2+19=19+2=3×7 8=（3 ）＋（5 ）

If x and y are independent random variables and their densities are FX (x) and FY (y), then the probability density of their sum z = x + y is FZ (z) =?

Answer:
fz(z) = fx * fy =∫{-∞,∞}fx(z-y)fy(y)dy = ∫{-∞,∞}fx(x)fy(z-x)dx
Where FX * FY denotes the convolution of FY (y) of FX (x)

It is known that the quadratic function f (x) = the square of AX + BX + C satisfies that the image passing through (0,3) g (x) = f (x) + 6x is an even function
If the equation f (x) = 0 has two equal roots, find the analytic expression of F (x)
② If the difference between the maximum value and the minimum value of F (x) (x ∈ [- 1,1]) is equal to 12, find the value set of A

F (0) = C = 3f (x) = ax & # 178; + BX + 3 G (x) = ax & # 178; + (B + 6) x + 3 = ax & # 178; - (B + 6) x + 3 = g (- x) B + 6 = - B-6 B = - 6F (x) = ax & # 178; - 6x + 31 symmetry axis is 3 / AF (6 / a) = 9 / A-18 / A + 3 = 0, a = 3, so f (x) = 3x & # 178; - 6x + 32 f (x) = ax & # 178; - 6x + 3 sum of two = 6 / A

How much is 69 times 33 / 70?

69*33/70
=3*23*33/70
=99*23/70
=(100*23-23)/70
=(2300-23)/70
=2277/70

（1）（7/a－5/4a)×2a （2）b÷(b/3－b/8）
calculation

General score (1) = 23 / 4A * 2A = 11.5
(2)=b*(24/5b)=4.8