How to do math problems well, how to do math problems?

The first sentence of the title indicates that the conversion relationship between the Cartesian coordinate system and the polar angle coordinate system satisfies the criteria, x= cos, y= sin

Curve c polar coordinate equation cos( -3)=1,==1 2*cos +sqrt(3) 2*sin )] 1，=>x+sqrt(3)y=2.This is the Cartesian coordinate equation for c.

Intersection m(2,0), n(0,2sqrt(3) scatter shed loss 3), p(1,sqrt(3) 3).

The straight line op, y=sqrt(3) 3*x, =sin =sqrt(3) 3* cos ,=6+k ,k is an integer.

Master Wang drove from A to B at a speed of 60 kilometers per hour, and the distance to A and B in 12 hours was 12x60=720 kilometers.

When he returned, he increased his speed, traveled 80 kilometers per hour, and returned to the first place in time: 720 80 = 9 hours.

The total distance is 12x60=720

So it takes 720 80 = 8

So it takes 9 hours.

I wish you progress in your studies and adopt oh, thank you.

Speed x Time = Distance.

Traveling at a speed of 60 kilometers per hour, arriving in 12 hours, that is, a total of 60 * 12 = 720 kilometers, the distance back and forth is the same, and it takes 720 80 = 9 hours to travel 80 kilometers per hour when returning.

60 12 = 720 (km) This is the total distance because speed x time = distance.

720 80 = 9 (hours) This is the time required, because 720 is the total distance, and 80 is the distance it travels per hour, that is, the speed, so (720) distance (80) speed = (9) time [from the title].

Distance = Speed x Time = 60x12 = 720km Time = Distance Time = 720 80 = 9 hours.

6. Let x=0 and y +6y-7=0

y-7）（y+1）=0

y=7 or y=-1

The distance is 7+1=8

D7 is selected, and the circle p can be reduced to (x-1) +y+4) =16, and the center of the circle (1, -4).

The circle q can be reduced to (x+3) +y =16 the center of the circle (-3,0) correct (substituting x=1 into the two equations gives y=0 and the intersection coordinates are (1,0)) correct (the radius is 4).

I checked the meaning of touch and ......Tangent, so wrong to choose B

6.Let x=0 have y +6y-7=0, and the ordinates of a and b are the two roots of the equation.

Therefore, (y-1)(y+7)=0,|ab|=|1-（-7）|=8

Choose D7Pick B

f'(x) = 3x -6x-9 = 3 (x - 3) (x + 1) let f'(x)=0, x=3 or -1

f(x) increases monotonically in the interval (- 1) (3,+) and decreases monotonically in the interval [-1,3].

So f(x) achieves a maximum value of 10 at x=-1

A minimum value of -22 is obtained at x=3

The example questions that the teacher has talked about must be done, the foundation is very important, as for the difficult and strange questions, you have the energy to specialize, and you have no energy to give up, after all, the exam looks at the score, not the ability, and the score of the problem is very small.

Analysis: There is no solution in decimal.

In the decimal system, 11 + 13 + 5 = 30

How can you add three odd numbers to get an even number? Turn 9 upside down to 6, add 11, add 13

The focus should be on two percent, the equation: 2 + 13 + 15 = 30