When n=______ The binomial 5 x 2Y 2n + 1 is the same as 13 y 3x 2

When n=______ The binomial 5 x 2Y 2n + 1 is the same as 13 y 3x 2

∵ 5x2y2n + 1 and 13y3x2 are of the same kind, ∵ 2n + 1 = 3, ∵ n = 1, so the answer is 1

8. The roots of equation x & # 178; - (2 + 3x) + 6 are 9. If equation AX & # 178; + BX + C = 0, then X1 + x2 =. X1 × x2=
8. The roots of equation x & # 178; - (2 + 3x) + 6 are
9. If the equation AX & # 178; + BX + C = 0, then X1 + x2 =. X1 × x2=

8) First of all, this is not an equation, but an algebraic expression. If it is equal to 0, then the equation has no real root. There are two imaginary roots: X1 = 3 / 2 + √ 7I / 2; x2 = 3 / 2 - √ 7I / 2
9）x1+x2=-b/a x1×x2=c/a

The equation x & # 178; - 2x + 1 = 4-3x is reduced to the general form, where a =, B =, C =, the root of the equation is

There is no ABC in this equation

The rounding method is used to approximate 0.05091, in which the error is ()
A. 0.1 (accurate to 0.1) b.0.05 (accurate to percentile)
C. 0.05 (keep two significant digits) d.0.0502 (accurate to 0.0001)

Use the rounding method to approximate 0.05091 according to the requirements. The error is (d)
A. 0.1 (accurate to 0.1) b.0.05 (accurate to percentile)
C. 0.05 (keep two significant digits) d.0.0502 (accurate to 0.0001)
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A 470 meter long train passes the 1030 meter long bridge in 1 minute and 20 seconds, and then passes a tunnel in 40 seconds at the same speed. How long is the tunnel?

1 minute 20 seconds = 80 seconds, [(470 + 1030) △ 80] × 40-470 = 18.75 × 40-470 = 750-470 = 280 meters; answer: the tunnel is 280 meters long

Additional questions: as shown in the figure, in the quadrilateral ABCD, point E is the midpoint of BC, point F is the midpoint of CD, and AE ⊥ BC, AF ⊥ CD. (1) proof: ab = ad; (2) please explore the quantitative relationship between ∠ EAF, ∠ BAE, ∠ DAF? And prove your conclusion

(1) It is proved that: connecting AC, ∵ point E is the midpoint of BC, AE ⊥ BC, ∵ AB = AC, ∵ point F is the midpoint of CD, AF ⊥ CD, ∵ ad = AC, ∵ AB = ad. (2) ∵ EAF = ∠ BAE + ∠ DAF. It is proved that ∵ AB = AC, that is, ∵ ABC is an isosceles triangle. ∵ AE ⊥ BC, (known), ∵ BAE = ∠ EAC (three lines of isosceles triangle in one)+ ∠FAC=∠BAE+∠DAF．

If the stars are one light year away, are we seeing the stars a year ago?

If the stars are one light year away, are we seeing the stars a year ago?
-----------It was a year ago!

There are two charging methods for mobile phones: A. pay the monthly rent of 22 yuan per month, and then charge by 0.2 yuan per minute; B. charge in July, and charge by 0.4 yuan per minute. May I ask: when is the monthly talk time, the cost of the two charging methods is the same? Under what circumstances is the monthly talk time saved by a method?

It is the same when the call time is equal to 110 minutes, and more than 110 minutes is appropriate

In trapezoidal ABCD, AB is parallel to CD, and BM is vertical to cm. M is the midpoint of AD?

Connect AC, make de parallel to AC, cross Ba extension line to e, then ACDE is parallelogram; be = AB + CD;
If ad is a diagonal of a parallelogram and M is the midpoint of AD, then CE must pass through point m (parallelogram diagonal bisection);
Because BM is perpendicular to cm, in triangle BCE, BM is both high and midline, then BCE is isosceles triangle, that is BC = be;
Then AB and CD are equal to BC;

How much is 1.0 times 10 to the third power kg per cubic meter

1kg / m3 = 0.001g/cm3, so 1.0 × 10 cubic kg / m3 = 1g / cm3