Tính
3(22 + 1) (24 + 1) (28 + 1) (216 + 1)
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a) Ta có: \(\left(2+1\right)\left(2^2+1\right)\left(2^4+1\right)\left(2^8+1\right)\left(2^{16}+1\right)\)
\(=\left(2-1\right)\left(2+1\right)\left(2^2+1\right)\left(2^4+1\right)\left(2^8+1\right)\left(2^{16}+1\right)\)
\(=\left(2^2-1\right)\left(2^2+1\right)\left(2^4+1\right)\left(2^8+1\right)\left(2^{16}+1\right)\)
\(=\left(2^4-1\right)\left(2^4+1\right)\left(2^8+1\right)\left(2^{16}+1\right)\)
\(=\left(2^8-1\right)\left(2^8+1\right)\left(2^{16}+1\right)\)
\(=\left(2^{16}-1\right)\left(2^{16}+1\right)\)
\(=2^{32}-1\)
\(3\left(2^2+1\right)\left(2^4+1\right)\left(2^8+1\right)\left(2^{16}+1\right)\)
\(=\left(2^2-1\right)\left(2^2+1\right)\left(2^4+1\right)\left(2^8+1\right)\left(2^{16}+1\right)\)
\(=\left(2^4-1\right)\left(2^4+1\right)\left(2^8+1\right)\left(2^{16}+1\right)\)
\(=\left(2^8-1\right)\left(2^8+1\right)\left(2^{16}+1\right)\)
\(=\left(2^{16}-1\right)\left(2^{16}+1\right)\)
\(=2^{32}-1\)
Ta có
N = ( 2 + 1 ) ( 2 2 + 1 ) ( 2 4 + 1 ) ( 2 8 + 1 ) ( 2 16 + 1 ) ( 2 16 + 1 ) = 3 ( 2 2 + 1 ) ( 2 4 + 1 ) ( 2 8 + 1 ) ( 2 16 + 1 ) = [ ( 2 2 – 1 ) ( 2 2 + 1 ) ] ( 2 4 + 1 ) ( 2 8 + 1 ) ( 2 16 + 1 ) = ( 2 4 – 1 ) ( 2 4 + 1 ) ( 2 8 + 1 ) ( 2 16 + 1 ) = ( 2 8 – 1 ) ( 2 8 + 1 ) ( 2 16 + 1 ) = ( 2 16 - 1 ) ( 2 16 + 1 ) = 2 16 2 − 1 = 2 32 − 1 M à 2 32 − 1 > 2 32 ⇒ N < M
Đáp án cần chọn là: A
\(A=3\left(2^2+1\right)\left(2^4+1\right)\left(2^8+1\right)\left(2^{16}+1\right)\)
\(=\left(2^2-1\right)\left(2^2+1\right)\left(2^4+1\right)\left(2^8+1\right)\left(2^{16}+1\right)\)
\(=\left(2^4-1\right)\left(2^4+1\right)\left(2^8+1\right)\left(2^{16}+1\right)\)
\(=\left(2^8-1\right)\left(2^8+1\right)\left(2^{16}+1\right)\)
\(=\left(2^{16}-1\right)\left(2^{16}+1\right)\)
\(=2^{32}-1\)
Đặt : \(P=\left(2^2-1\right)\left(2^2+1\right)\left(2^4+1\right)\left(2^8+1\right)\left(2^{16}+1\right)\)
\(=\left(2^4-1\right)\left(2^4+1\right)\left(2^8+1\right)\left(2^{16}+1\right)\)
\(=\left(2^8-1\right)\left(2^8+1\right)\left(2^{16}+1\right)\)
\(=\left(2^{16}-1\right)\left(2^{16}+1\right)\)
\(=2^{32}-1\)
`A=(2-1)(2+1)(2^2+1)...(2^16+1)`
`=(2^2-1)(2^2+1)....(2^16+1)`
`=(2^4-1)....(2^16+1)`
`=2^32-1<2^32`
`=>A<B`
1,
Đặt \(A=\left(2+1\right)\left(2^2+1\right)\left(2^4+1\right)\left(2^8+1\right)\left(2^{16}+1\right)\)
\(\left(2-1\right)A=\left(2-1\right)\left(2+1\right)\left(2^2+1\right)\left(2^4+1\right)\left(2^8+1\right)\left(2^{16}+1\right)\)
\(1A=\left(2^2-1\right)\left(2^2+1\right)\left(2^4+1\right)\left(2^8+1\right)\left(2^{16}+1\right)\)
\(A=\left(2^4-1\right)\left(2^4+1\right)\left(2^8+1\right)\left(2^{16}+1\right)\)
\(A=\left(2^8-1\right)\left(2^8+1\right)\left(2^{16}+1\right)\)
\(A=\left(2^{16}-1\right)\left(2^{16}+1\right)\)
\(A=2^{32}-1\)
Vậy \(A=2^{32}-1\)
2, \(x^2-6x=-9\)
\(x^2-6x+9=0\)
\(\left(x-3\right)^2=0\)
\(x-3=0\)
\(x=3\)
Vậy \(x=3\)
Câu 21: So sánh M = 232 và N = (2 + 1)(22 + 1)(24 + 1)(28 + 1)(216 + 1)
A. M > N B. M < N C. M = N D. M = N – 1
Câu 22: Tìm giá trị lớn nhất của biểu thức B = 4 – 16x2 – 8x
A. 5 B. -5 C. 8 D.-8
Câu 23: Biểu thức E = x2 – 20x +101 đạt giá trị nhỏ nhất khi
A. x = 9 B. x = 10 C. x = 11 D.x = 12
Câu 24: Kết quả của phép chia 15x3y4 : 5x2y2 là
A. 3xy2 B. -3x2y C. 5xy D. 15xy2
Câu 25: Kết quả của phép chia (6xy2 + 4x2y – 2x3) : 2x là
A. 3y2 + 2xy – x2 B. 3y2 + 2xy + x2 C. 3y2 – 2xy – x2 D. 3y2 + 2xy
$(6x+1)^2+(6x-1)^2-2(1+6x)(6x-1)$
$=(6x+1)^2+(6x-1)^2-2(6x+1)(6x-1)$
$=[(6x+1)-(6x-1)]^2$
$=2^2$
$=4$
b)$3(2^2+1)(2^4+1)(2^8+1)(2^{16}+1)$
$=3(2^2+1)(2^4+1)(2^8+1)(2^{16}+1)$
$=3\cdot\dfrac{2^4-1}{2^2-1}\cdot\dfrac{2^8-1}{2^4-1}\cdot\dfrac{2^{16}-1}{2^8-1}\cdot\dfrac{2^{32}-1}{2^{16}-1}$
$=3\cdot\dfrac{2^{32}-1}{2^2-1}$
$=3\cdot\dfrac{2^{32}-1}{3}$
$=2^{32}-1$
$x(2x^2-3)-x^2(5x+1)+x^2$
$=2x^3-3x-5x^3-x^2+x^2$
$=2x^3-5x^3-3x$
$=-3x^3-3x$
$=-3x(x^2+1)$
d)$3x(x-2)-5x(1-x)-8(x^2-3)$
$=3x^2-6x-5x+5x^2-8x^2+24$
$=3x^2+5x^2-8x^2-11x+24$
$=-11x+24$
$=24-11x$
\(3\left(2^2+1\right)\left(2^4+1\right)\left(2^8+1\right)\left(2^{16}+1\right)\)
\(=\left(2^2-1\right)\left(2^2+1\right)\left(2^4+1\right)\left(2^8+1\right)\left(2^{16}+1\right)\)
\(=\left(2^4-1\right)\left(2^4+1\right)\left(2^8+1\right)\left(2^{16}+1\right)\)
\(=\left(2^8-1\right)\left(2^8+1\right)\left(2^{16}+1\right)=\left(2^{16}-1\right)\left(2^{16}+1\right)=2^{32}-1\)
sao lớp 8 khó quá vậy