=6y/( 12x^2y^2)+8y^2/( 12x^2y^2)-9x/( 12x^2y^2)
=(6y+8y^2-9x)/( 12x^2y^2)
(2) the square of x-the square of y at xy point+the +y-x point of x.
=y^2/x(x-y)-x^2/x(x-y)
=(y^2-x^2)/x(x-y)
=-(y+x)/x
(3)a+ 1 a square-1 a square +2 times a square +4a+4 A a square -2a+ 1
= 1/(a+ 1)-(a+2)/(a^2- 1)*(a- 1)^2/(a+2)^2
= 1/(a+ 1)-(a- 1)/(a+2)(a+ 1)
=(a+2-a+ 1)/(a+2)(a+ 1)
=3/(a+2)(a+ 1)
(4) (x+65438+ 1-x- 1) divided by 1-2.
=(x- 1-x- 1)/(x^2- 1)*( 1-x)/2
= 1/(x+ 1)
(7) the square of x-1+x+1+2-x-1+1.
=2/(x^2- 1)+(2x-2)/(x^2- 1)-(x+ 1)/(x^2- 1)
=(x- 1)/(x^2- 1)
= 1/(x+ 1)
(8) Party A-Party B+Party A-2A+Party 2B-A-B.
=(2a^2+2b^2)/2(a^2-b^2)-(a-b)^2/2(a^2-b^2)
=(a+b)^2/2(a^2-b^2)
=(a+b)/2(a-b)
1. If a2+a- 1=0 is known, then a3+2a2+3=
2. The result of simplification is _ _ _ _ _ _ _ _ _,
3. The price of a commodity is 120 yuan. If the goods are sold at a reduced price of 90% of the marked price and there is still a profit of 20% relative to the purchase price, the purchase price of the goods is RMB.
In April and May, several teachers from our school traveled to Hangzhou and stayed at night. If there are 4 people in each room, the remaining 20 people have no dormitory. If the number of dormitory rooms is three, the number of teachers is six.
5. As shown in the figure, in the rectangular ABCD, AB=6cm, BC=8cm,
Now fold the rectangle so that point B coincides with point D, and then fold EF.
The length is centimeters.
6. If the height of the base of the isosceles triangle is greater than 18cm and the median line of the waist is equal to 15cm, the area of the isosceles triangle is equal to.
7. If the integer part of is a and the decimal part is b, the size of is _ _ _ _ _ _ _ _.
8. The distances from each point to three sides in a right triangle are equal, all D, and the length of the hypotenuse is C, so the area of the right triangle is _ _ _ _ _ _ _ _ _.
9. Assessment:
10, several students lined up in a row, first from left to right 1 count off, and the rightmost student reported 2; Then from right to left, 1 counts off to 4, the leftmost student counts off to 3, and the students of 128 count off to 1 twice, so there are always * * * students.
1, if a=x+ 1 and b=x+2, the value of a2+b2+c2-ab-bc-ac is ().
A 0 B 1 C 2 D 3
2. It is known that ax+a-x=2, and the value of a2x+a-2x is ().
A 4 B 3 C 2 D 6
3. it is known that: C > 1, x= c- c- 1, y= c+ 1- c, z= c+2- c+ 1, then the relationship between x, y and z is ().
A x>y>z B z >x>y C y>x>z D z >y >x
4. There are points () on the plane with the same distance from the straight line where the three sides of △ABC are located.
A 1 B 2 C 3 D 4
5. Take 4m+5,2m-1,20m as the integer m*** and the length of three sides of the triangle ().
A 2 B 6 C 12 D 18
6. A triangle surrounded by a straight line where the bisectors of the three outer corners of the triangle are located.
Yes ()
Triangle b, obtuse triangle c, right triangle
D, right-angled or obtuse triangle
7. As shown in the figure, take a point E on the isosceles right angle △ABC, ∠ BAC = 90, AD‖BC, AD.
Let ∠ EBC = 30, then the relationship between be and BC is ()
A, be > BC b, be < BC c, BE=BC D, uncertain.
8. As shown in the figure, in a square ABCD, AB=8, Q is the midpoint of the CD, let ∠DAQ=a, take a point P on the CD, and let ∠BAP=2a, then the length of CP is equal to ().
a、 1 B、2 C、3 D、
9. If the right side of a right triangle is 1 1 and the other two sides are natural numbers, then its circumference is ().
a、 132 B、22 C、7 1 D、72
10, as shown in the figure on the right, translate the △ABC with the area of 12㎝ to the position of △DEF along BC, and the translation distance is twice that of the side BC, then the area of the quadrangle in the figure is ().
A, 24cm b, 36cm c, 48cm
1, the OM and ON highways intersect at an angle of 300, and there is a primary school 80 meters along the OM highway (pictured).
When the tractor is driving in the ON direction, the roadside is 50 meters away from the noise. It is known that the speed of tractor is 18 km/h,
Is the school affected by noise? If so, when? If it is not affected, explain.
2. As shown in figure 12, in the isosceles trapezoid ABCD, diagonal AC and BD intersect at O, ∠ ACD = 60, and points S, P and Q are the midpoints of OD, OA and BC respectively. (1) proves that △PQS is an equilateral triangle; (2) If AB=5 and CD=3, find the area of △PQS; (3) If the ratio of the area of △PQS to the area of △AOD is 7: 8, find the ratio CD of the upper and lower bottoms of the trapezoid: