Question 145. Sophomore math problems. Pick a few. Don t pick randomly. It s about the final grades.

x +y +4x-5=0 to (x+2) +y =9 center coordinates (-2,0) with a radius of 3

x + y -12x-12y + 23 = 0 to (x-6) + (y-6) = 9 center coordinates (6,6) with a radius of 7

The center distance of the second circle: under the root number (-2-6) +0-6) = 10 radius of the second circle and 3+7 = 10

So the two circles are cut outward. i.e. choose B

x +y -4x+6y-3=0 is (x-2) +y+3) =16 center coordinates (2,-3) and the radius is 4

Let the equation of the circle be (x-2) +y+3) =r point (-1,1).

1-2）²+1+3）²=r²

i.e. r = 25

Therefore, the equation for the circle is (x-2) +y+3) =25, i.e., a is chosen

15 questions choose A.

x-2) 2+(y+3) 2 is centered on a or b, and then -1,1 is brought into a and b to get the form a.

14 questions choose D, it is easy to get to the center of the circle is 10, and the radius is 9, so it is separated.

15 questions choose A, judge a and b according to the center of the circle, and bring in (-1,1) to get answer A

14.Tangent. The centers of the two circles are (-2,0)(6,6), the center distance is 10, and the radius of the two circles is 3,7, respectively

Then the sum of the radii is equal to the centricity of the circle, and the two circles are tangent.

The center beam of the circle with the center of (2,-3) is (x-2) 2+(y+3) 2+c=0, and (-1,1) is brought into the equation by c=-25 to obtain a

First of all, a and d can be excluded according to x=0 and y=0, and then in b and c, the intersection point of the two straight lines is (1, m+n), and according to the straight line, m+n can be judged to be a positive value, so the answer is b

, 225 degrees.

45 degrees, 6 don't know what is Yu tilt, only a little bit, sorry.

9 question selection a, because the intercept with the y axis is 2, that is, when x=0, y=2, x=0 into various formulas, only l1 and l4 meet the requirements, but the slope is 3, and the slope of l4 is -2 3, which also does not meet the requirements, so only l1 meets, so choose a

I'll help the landlord answer it

Solution: The answer is A, 1, which is L1. Here's the answer:

Straighten the line as: y=kx+b.

l1：y=3x+2

l2：y=-3x-2

l3：y=-x/3-2/3

l4：y=-2x/3+2

Obviously, only L1 has a slope of 3 and an intercept of 2 on the y-axis.

I hope it will be helpful to the landlord o(o

Question 9:

Select Analysis:

The slope of l1 is 3

The slope of L2 is -3

The slope of l3 is -1 3

The slope of l4 is -2 3

So choose A

Nine questions choose AChoose C for ten questions, you can't go wrong, remember to add points.