Grade seven math problems. Help to give points Grade 7 Volume 2 full channel Beijing Normal University Edition 16 pages Given x + y = 6, x minus y = 5, find the square of x minus the square of Y Solving equations, (writing process) (3x + 4) times (3x minus 4) = 9 (x minus 2) (x + 3)

X²-Y²=(X+Y)(X-Y)=6*5=30
（3X+4）*（3X－4）=9（X－2）（X+3）
9X²-16=9(X²+X-6)
9X²-16=9X²+9X-54
9X=54-16=38
X=38/9

Class 7 (11) bought 80 notebooks together, which cost 205 yuan, including 3 yuan for each type a notebook and 2 yuan for each type B notebook?

Let a and B buy X and Y notebooks respectively. According to the meaning of the question, x + y = 803x + 2Y = 205, the solution is x = 45y = 35. Answer: A and B buy 45 and 35 notebooks respectively

Excellent math problems in the second semester of grade seven

3.72 * 49 + 37.2 * 5.1 + 49 * 51 =? Simple calculation!

3.72×49+37.2×5.1+49×51
＝37.2×﹙4.9＋5.1﹚＋﹙50－1﹚×﹙50＋1﹚
＝372＋2500－1
＝2871.

12 points = 27 points = 0.75 = 36 points = 72 points

9 out of 12 = 27 out of 36 = 0.75 = 36 out of 48 = 54 out of 72

Given that the function g (x) = - x2-3, f (x) is a quadratic function, when x ∈ [- 1,2], the minimum value of F (x) is 1, and f (x) + G (x) is an odd function, the analytic expression of F (x) is obtained

Let f (x) = AX2 + BX + C (a ≠ 0), then f (x) + G (x) = (A-1) x2 + BX + C-3, ∵ f (x) + G (x) is an odd function, ∵ a = 1, C = 3 ∵ f (x) = x2 + BX + 3, symmetry axis X = - B2, when - B2 > 2, that is, B < - 4, f (x) is a decreasing function on [- 1, 2], and the minimum value of ∵ f (x) is f (2

7 / 9 △ 13 / 5 + 2 / 9 × 5 / 13

7/9÷13/5+2/9×5/13
=7/9× 5/13+2/9×5/13
=（7/9+2/9)×5/13
=1×5/13
=5/13

Lim tends to 0, sin MX is NX

LIM (x tends to 0) NX / sin (MX)
=LIM (x tends to 0) n / m * [MX / sin (MX)]
Now x tends to zero, so does MX
So we can know from the important limit that the limit value of MX / sin (MX) is 1,
that
Original limit
=LIM (x tends to 0) n / m * [MX / sin (MX)]
= n/m

3X=0.393÷3.

1.3x＝0.393÷3.2
x＝0.393÷3.2÷1.3
x＝393÷4160
x＝393/4160

555×0.5

277.5

Grade seven math problems. Help to give points Grade 7 Volume 2 full channel Beijing Normal University Edition 16 pages Given x + y = 6, x minus y = 5, find the square of x minus the square of Y Solving equations, (writing process) (3x + 4) times (3x minus 4) = 9 (x minus 2) (x + 3)