Simple calculation: 63 × 27 + 19 × 21

63×27+19×21
=21×81+19×21
=21×(81+19)
=21×100
=2100

Let the values of a, B and C be 15, 18 and 19 respectively. After the expression x = a + b > C & & C + +, x = 1 and C = 20
What I don't understand is in a + b > C & & C + +&&

That's what it means to be with you

It is known that when x = 1, the quadratic function has a maximum value of 2 and passes through the point (2, - 3)

The vertex of the parabola is (1,2)
Let the analytic expression be:
y=a(x-1)^2+2
Over point (2, - 3), substituting, with
a(2-1)^2+2=-3
a=-5
y=-5(x-1)^2+2

It is known that a straight line passing through point P (2,0) with a slope of 4 / 3 and a parabola y ^ 2 = 2x intersect at two points a and B. let the midpoint of line AB be m. find the mark of point M
Is to use the parametric equation to solve!

From the straight line passing through the point P (2,0), the slope is 4 / 3, the linear equation is x = t + 2Y = 4 / 3T, which is substituted into the parabola y ^ 2 = 2x, 16 / 9t ^ 2 = 2 * (T + 2) is reduced to 8t ^ 2-9t-18 = 0, and the coordinates of the midpoint m of T1 + T2 = 9 / 8 segment AB are (x1 + x2) / 2 = (T1 + T2) / 2 + 2 = 9 / 16 + 2 = 41 / 16 (Y1 + Y2) / 2 = 4 / 3 * (T1 + T2) / 2 =

1. The passenger car and the freight car run from a and B with a distance of 530 km at the same time. The passenger car runs 90 km per hour. After a few hours, the two cars are 56 km apart?
2. Two people set out from two places 90 meters apart at the same time and walk backward. The speed of a is 75 meters per minute, and that of B is 72 meters per minute. A few minutes later, they are 972 meters apart?
If you can answer the first question, you must answer the second

2. After X minutes, the distance between them is 972 meters, 75X + 72x + 90 = 972, 147x = 882, x = 6 minutes

In the space rectangular coordinate system, given the points a (1,0,2), B (1, - 3,1), the point m is on the Y axis, and the distance from m to a and B is equal, then the coordinate of M is ()
A. （0，-1，0）B. （0，1，0）C. （1，0，1）D. （0，1，1）

Let m (0, y, 0) get y = - 1 from 12 + Y2 + 4 = 1 + (y + 3) 2 + 1, so m (0, - 1, 0) is selected: a

1. (a + 3b) (a-3b) - (2a-b)
2. - 3x-42xy + 96y
3. (X-Y) fang-4 (x-y-1)

(A+3B）（A－3B）-（2A-B）²
=A²-9B²-4A²-B²+4AB
=-(3A²-4AB+10B²）
=-
-3X²-42XY+96Y²
=-3（X²+14XY-32Y²）
=-3（x+2y）（x-16y）
（X-Y）²-4（X-Y-1）
=（X-Y）²-4（x-y）+2²
=（x-y-2）²

The reason for the decrease of cultivated land and the increase of grain yield
comprehensive

1. The increase of population makes the cheap labor increase;
2. The progress of science and technology has improved the varieties of crops;
3. The progress of science and technology has improved the technology of controlling crop diseases and insect pests;
That's all for the moment

The distance between the reflection and the shooter is ()
A.340m B.680m C.1360m D.2420m

The time is 2S
Speed 340m / S
The distance (2 × 340) / 2 = 340m, because it goes and comes back, it is twice the distance and needs to be divided by 2
A.340m

If April 1 is a Tuesday, April 28 is a day of the week? How to calculate this problem

There are seven days in a week
It's a seven day cycle
Then 1, 8, 15, 22 and 29 should be Tuesdays
28 was the day before 29
The 28th should be Monday

Simple calculation: 63 × 27 + 19 × 21