Cho biểu thức: 38756 x 9 . Biểu thức nào sau đây có giá trị bằng biểu thức đã cho?
A. 9x37856
B. 9x38765
C. 9x37865
D. 9x38756
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Ta có: 375+28=28+375
Vậy biểu thức có giá trị bằng với biểu thức 375+28 là 28+375.
Đáp án B
Đáp án D
Phương pháp: Sử dụng công thức (giả sử các biểu thức là có nghĩa)
Cách giải:
99999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999+999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999+999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999
Nguyễn Tất Phúc ko đăng linh tinh
Tl cho đàng hoàng
Còn ko biết TL thì ko nên TL
HT
a) x ≠ 0 , x ≠ − 2
b) Ta có D = x 2 - 2x - 2.
c) Chú ý D = - x 2 - 2x - 2 = - ( x + 1 ) 2 - 1 ≤ -1. Từ đó tìm được giá trị lớn nhất của D = -1 khi x = -1.
a: Khi x=5 thì A=5/(5+3)=5/8
b: \(C=A+B=\dfrac{x}{x+3}+\dfrac{2}{x-3}+\dfrac{3-5x}{x^2-9}\)
\(=\dfrac{x^2-3x+2x+6+3-5x}{\left(x-3\right)\left(x+3\right)}=\dfrac{x^2-6x+9}{\left(x-3\right)\left(x+3\right)}=\dfrac{x-3}{x+3}\)
c: Để C nguyên thì x+3-6 chia hết cho x+3
=>\(x+3\in\left\{1;-1;2;-2;3;-3;6;-6\right\}\)
=>\(x\in\left\{-2;-4;-1;-5;0;-6;-9\right\}\)
Khi đổi chỗ các thừa số trong một tích thì tích đó không thay đổi.
Do đó ta có: 38756×9=9×38756
Vậy biểu thức có giá trị bằng với biểu thức 38756×9 là 9×38756.
Đáp án D