Given x2 + X - 1 = 0, find the value of X3 + 2x2 + 3

Given x2 + X - 1 = 0, find the value of X3 + 2x2 + 3

According to the meaning of the question: x2 + x = 1, ｜ X3 + 2x2 + 3, = X3 + x2 + x2 + 3, = x (x2 + x) + x2 + 3, = x + x2 + 3, = 4; or: according to the meaning of the question: x2 + x = 1, so, X3 + 2x2 + 3, = X3 + x2 + x2 + 3, = x (x2 + x) + x2 + 3, = x + x2 + 3, = 1 + 3, = 4

Given that x − 1x = 3, then the value of the polynomial x3-x2-7x + 5 is______ ．

∵ x-1x = 3, ∵ x2-1 = 3x, x-3 = 1X, ∵ x3-x2-7x + 5 = x3-7x-x2 + 5 = x (x2-7) - x2 + 5 = x (3x-6) - x2 + 5 = 2x2-6x + 5 = 2x (x-3) + 5 = 2x · 1x + 5 = 2 + 5 = 7

If the quadratic polynomial x2 + 2kx-3k2 can be divided by X-1, then the value of K is______ ．

∵ the polynomial x2 + 2kx-3k2 can be divided by X-1, ∵ X-1 is the factor of the polynomial x2 + 2kx-3k2, ∵ X-1 = 0, that is, x = 1 is the solution of the polynomial x2 + 2kx-3k2, ∵ 12 + 2k-3k2 = 0, solving the univariate quadratic equation about K, we get K1 = 1, K2 = - 13, so the answer is: k = 1 or K = - 13

The new operation symbol * is defined, and the operation rule is a * b = 1A / 2-1B / 4. 1. Find the value of 5 * (- 5) 2. Solve the equation, 2 * (2 * χ) = 1 * χ

（1）5*(-5)=1/2 ×5-1/4 ×（-5）＝15/4
（2）2*（2*χ）=1*χ
2*（1/2 ×2-1/4 X）=1/2 ×1-1/4 X
2*（1- 1/4 X）=1/2 -1/4 X
1/2 ×2-1/4 (1- 1/4 X）=1/2 -1/4 X
1-1/4 +1/16X=1/2 -1/4 X
5/16X=-1/4
X=-4/5
Or (2) 2 * (2 * χ) = 1 * χ
1/2 ×2- 1/4（2*χ）=1/2 ×1-1/4 X
1- 1/4 (1- 1/4 X）=1/2 -1/4 X
1-1/4 +1/16X=1/2 -1/4 X
5/16X=-1/4
X=-4/5

It takes 10 hours for a bus and 15 hours for a freight car to go from a to B. now the two cars leave each other from two places. When they meet, the bus runs 240 kilometers. How many kilometers are there between a and B?

A: the distance between a and B is 400 km

What's five out of three of eight

40/3

A and B go from a to B. A walks for 2 hours before B starts. As a result, B is 15 minutes later than A. A's speed is 4 km / h, and B's speed is 6 km / h
Then the equation can be established_______________ .

X / 4-2 = x / 6 + 1 / 4 is the time a leaves minus two hours, which is equal to the time B leaves plus a quarter of an hour

X + 1 / 2 (x-1) = 9 solution equation

X + 1 / 2 X-1 / 2 = 9 / 2 3x = 19 / 2 x = 19 / 3

Given three points a (1, - 1) B (4, - 2) C (- 2,0), it is proved that A.B.C three points are collinear

Certification:
Vector method
A(1,-1) B(4,-2) C(-2,0)
The vector AB = (3, - 1)
Vector AC = (- 3,1)
‖ vector AB / / vector AC
A.B.C three points collinear

The sum of a and B is 11.63. Xiaoqiang moved the decimal point of an addend to the left one place due to carelessness. The result is 5.87?

And less
11.63－5.87＝5.76
The decimal point of an addend is moved one place to the left, which is reduced by 10 times, 0.1 of the original number, less than the original number
1－0.1＝0.9
So this is the addend
5.76÷0.9＝6.4
The other addend is
11.63－6.4＝5.23