3. What does the letter1stand for?

1.D. 2.C. 3 65%m. 4。 (7a+4b)。

5.(30-2a)(20-2a)。 6.。

3.2 algebraic expression

1.C。 +2.4.。

5.(a+b)，(2a+4b)， 12，38。 6.B。

7.( 1) The seedling height in the fourth year is 160 cm.

(2)h = 100+ 15a；

(3) Substitute a =20 into 100+ 15a,

Get100+15× 20 =100+300 = 400 (cm).

So after 20 years of growth, the height of this tree is 400 cm.

3.3 Algebraic evaluation

1 . c 2。 -73.3.5.4.,60%.

5.( 1) ; (2) The store earned 1 170 yuan.

6.( 1)a(a+b)-π[a2+B2+(a-b)2]； (2)450 yuan.

3.4 Merge similar projects

1.D

4.( 1)-7x+3y； (2) .

5. When 5.x = 2 and y =-3, the original formula =-27.

6.( 1)4x+ 1-x-x-2 = 2x- 1；

(2) The original formula = 2× (- 1)- 1 =-3.

7.( 1) * * Finish the station two days ago;

(2) On the third day, 32 units must be completed before delivery can be made on time.

3. 1 ~ 3.4 test questions

ground stabilization

1 . a 2 . d 3 . c 4 . c 5 . a 6 . b

7.8.8.(2x-5)。 9. 102 a- 1.509。

10.207. 1 1.-2 0 10. 12.b=5.5a。

13.( 1)3x-y； (2)4x2y。

14. Original formula =, when x=, original formula =.

15. Because it is similar to,

So m=3 and n=2. = 2.

When m=3 and n=2, the original formula = 9-4 = 5.

16.( 1) 15a+(30- 15)×2a = 15a+30a = 45a；

(2) When a=4.98, 45a=45×4.98=224. 1 (yuan).

17.( 1) =, and the area of the intersection is () square meters.

(2) = 600-50× 2+2× 2 = 504, and the lawn (shaded part) covers an area of 504 square meters.

Improve ability

1

4.( 1) The living room area is m2, the bathroom area is m2, the bedroom area is 12m2, and the kitchen area is 6m2, so the total construction area is () m2.

(2) when, when, the total area of the ground is

(m ^ 2)。

Therefore, the total cost of paving floor tiles is (yuan).

5. The number of (1) regular pentagons is1,2, 3 in turn;

The number of triangles is 0,5, 10.

(2)5(n- 1)。

(3) No, because 5 (n- 1) is a multiple of 5.

246 is not divisible by 5.