Speed, 9th Grade Math! Ask for a master! 10

It's very simple, connect Co, B= Bco, Bco+ CoA= CoA+ ACE=90°, and because BCA= E=90°, the triangle BCA is similar to CEA, so BAC= CAD, arcBC=arcCD, BC=CD

What is this question? What?

l order. 2x+b=x 2-2x+3, i.e. x 2-4x+3-b=01; When a public point is lost, Delta=0, then b=-1

2;Two common points when Delta 0 b>-1

2 makes 2x+b=-2 x (x is not equal to zero), i.e. 2x 2+bx+2=0, a common point is Delta.

0 is b = 4, -4

Two are Delta 0 ie.

b> cha joke 4 or b<-4

Bring back verification. OK.

Connect MA, NA

ab=ac,∠a=120°

b=∠c=30°

b=∠bam=30°,∠c=∠can=30°∴∠bma=120°,∠cna=120°

amn=60°,∠anm=60°

The triangle amn is an equilateral triangle.

ma=na=mn

bm=ma,na=nc

bm=mn=nc

The perpendicular bisector of AB intersects BC to M, AB to E, and the perpendicular bisector of AC intersects BC to N and AC to F

In the triangle ABC, AB = AC, angle A = 120° angle B = angle C = 30 ° BM = AM, an = CN, angle CMA = angle B + angle MAB = 60°

Angle ANB = Angle C + Angle NAC = 60° Triangle AMN is a regular triangle, AN=AM=MN

bm=mn=nc

Angle b = angle c = angle bam = angle nac = 30 degrees, angle man = amn = anm = 60 degrees, , edge am=mn = an, and because the edge bm = am = an=nc, so the three sides are equal.

Variance formula: s 2 = [(x1 2+x2 2+.xn 2)-nx 2] n, (x represents the average).

From the title: s=2,x1 2+x2 2+.xn 2 = 61n substitution:

4=[61n-nx^2]/n=61-x^2x^2=57

That is, the square of the mean is 57.

Set up x car A, 3x 13,.

Need car B (13-3x) 2 cars, the freight is 50x+40 * [(13-3x) 2] = 260-10x, take x=4, get car B, not an integer, rounded off.

When taking x=3, get 2 cars B, which is in line with the title.

The freight is the most economical, which is 260-3x10=230 yuan.

That's it!

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