Khong tinh ket qua cua tung bieu thuc hay dien dau ( > , < , = ) vao cho cham
a) 12 x ( 367 + 82 ) . . . 82 x 12 + 12 x 367
b) ( 175 - 26 ) x 17 . . . 17 x 177 - 17 x 26
Nho giai thich nhe !
Ai nhznh mk tk !
Khong tinh ket qua hay dien dau >, <, = thich hop vao o trong co giai thich
a) 7/9+11/13+24/25 ... 3
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b)9/8+13/12+15/13+5/4 ... 4
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a) Ta thấy: 7/9<1, 11/13<1, 24/25<1 nên 7/9+11/13+24/25<3
b) Ta thấy: 9/8>1, 13/12>1, 15/13>1, 5/4>1 nên 9/8+13/12+15/13+5/4>4
1.tinh gia tri cua bieu thuc
a)45 x 789 +15 x 263 + 60 x 789 - 10 x 789
b)234 x 17 + 34 x 117 + 198 x 78
giup mk nhe thanks
a) 45 x 789 + 15 x 263 + 60 x 789 - 10 x 789 = 35505 + 3945 + 47340 - 7890
= 39450 + 47340 - 7890
= 86790 - 7890
= 78900.
b) 234 x 17 + 34 x 117 + 198 x 78 = 3978 + 3978 + 15444
= 7956 + 15444
= 23400.
k nha
tinh gia tri cua cac bieu thuc sau roi so sanh cac ket qua tinh duoc
(-25)-(-12), 18+(14-42), (-18)-13+17
(-25)-(-12)= - 13
18+(14-42)=18+(-28) = -10
(-18)-13+17=(-31) +17= -14
\(\rightarrow\)-13 < -10 > -14\(\Rightarrow\) (-25)-(-12) < 18+(14-42) > (-18)-13+17
chung minh rang cac bieu thuc sau khong phu thuoc vao gia tri cua bien x, biet B= x (x^3 + 2x^2 - 3x +2) - (x^2+ 2x) x^2 +3x ( x-1) +x-12
B=x^4+2x^3-3x^2+2x-x^4-2x^3+3x^2-3x+x-12
=-12
\(B=x\left(x^3+2x^2-3x+2\right)-\left(x^2+2x\right)x^2+3x\left(x-1\right)+x-12\)
\(=x^4+2x^3-3x^2+2x-x^4-2x^3+3x^2-3x+x-12\)
\(=\left(x^4-x^4\right)+\left(2x^3-2x^3\right)+\left(-3x^2+3x^2\right)+\left(2x-3x+x\right)-12\)
\(=0+0+0+0-12\)
\(=-12\)
cho pt: x^2-12x+4=0 c hai nghiem phan biet x1,x2. Khong giai pt, hay tinh gia tri cua bieu thuc: T=x1^2+x2^2/canx1+can x2cho pt: x^2-12x+4=0 c hai nghiem phan biet x1,x2. Khong giai pt, hay tinh gia tri cua bieu thuc: T=x1^2+x2^2/canx1+can x2
Ta có: \(\Delta'=32>0\)
\(\Rightarrow\) Phương trình có 2 nghiệm phân biệt
Theo Vi-ét, ta có: \(\left\{{}\begin{matrix}x_1+x_2=12\\x_1x_2=4\end{matrix}\right.\)
Mặt khác: \(T=\dfrac{x_1^2+x^2_2}{\sqrt{x_1}+\sqrt{x_2}}\)
\(\Rightarrow T^2=\dfrac{x_1^4+x^4_2+2x_1^2x_2^2}{x_1+x_2+2\sqrt{x_1x_2}}=\dfrac{\left(x_1^2+x_1^2\right)^2}{x_1+x_2+2\sqrt{x_1x_2}}\) \(=\dfrac{\left[\left(x_1+x_2\right)^2-2x_1x_2\right]^2}{x_1+x_2+2\sqrt{x_1x_2}}=\dfrac{\left(12^2-2\cdot4\right)^2}{12+2\sqrt{4}}=1156\)
Mà ta thấy \(T>0\) \(\Rightarrow T=\sqrt{1156}=34\)
Tìm x:
a) \(\dfrac{-12}{17}\) < \(\dfrac{x}{17}\) < \(\dfrac{-8}{17}\)
b) \(\dfrac{-1}{2}< x< \dfrac{5}{3}\)
c) 3,456 < x \(\le\) 7,89
d) 5,82 < \(\overline{\text{5,8x0}}\) < 5,845
e) 32, 82 < \(\overline{\text{3x, 850}}\) < 35,845
a) \(\dfrac{-12}{17}< \dfrac{x}{17}< \dfrac{-8}{17}\)
\(\Rightarrow-12< x< -8\)
\(\Rightarrow x\in\left\{-11;-10;-9\right\}\)
b) \(\dfrac{-1}{2}< x< \dfrac{5}{3}\)
\(\Rightarrow\dfrac{-3}{6}< x< \dfrac{10}{6}\)
\(\Rightarrow x\in\left\{\dfrac{-2}{6};\dfrac{-1}{6};0;\dfrac{1}{6};...;\dfrac{7}{6};\dfrac{8}{6};\dfrac{9}{6}\right\}\)
c) \(3,456< x\le7,89\)
\(\Rightarrow x\in\left\{3,456;3,457,3,458;...;7,89\right\}\)
d) \(5,82< \overline{5,8x0}< 8,845\)
\(\Rightarrow x\in\left\{3;4\right\}\)
e) \(32,82< \overline{3x,850}< 35,845\)
\(\Rightarrow x\in\left\{3;4\right\}\)
chung to bieu thuc khong phu thuoc vao gia tri cua bien
a)(x-1)(x+1)(x2+1)-(x-2)(x+2)(x2+4)
b)(3x-1)(2x+7)-(x+1)(6x-5)-(18x-12)
khong thuc hien phep tinh , neu du doan ket qua tim x:
a) x+ 8,75 = 8,75 ; x=............vi .......................................
b) 3/4 +x=12/16 ; x= .............vi...........................................
a) y=0 vì 0 cộng số nào chính là tổng thì được tổng chính bằng số hạng kia.
b) x=0 vì ta rút gọn: 12/16=3/4 mà 0 cộng số nào chính là tổng thì được tổng chính bằng số hạng kia.
Mình trả lời trước nè, .
ca hai x đều la 0 vi 0 cong voi so nao cung bang chinh no
Tìm STN x biết.
70 - 5. (X-3) = 45
12+ (5+x) = 20
130-( 100+x) = 25
175 + (30 - x) = 200
5(x + 12) + 22 = 92
95-5(x+2) = 45
14x +54 = 82
15x -133 = 17
155-10(x + 1) = 55
1) 70 - 5( x - 3 ) = 45
5( x - 3 ) = 70 - 45
5( x - 3 ) = 25
x - 3 = 25 : 5
x - 3 = 5
x = 5 + 3
x = 8
2) 12 + ( 5 + x ) = 20
5 + x = 20 - 12
5 + x = 8
x = 8 - 5
x = 3
3) 130 - ( 100 + x ) = 25
100 + x = 130 - 25
100 + x = 105
x = 105 - 100
x = 5
4) 175 + ( 30 - x ) = 200
30 - x = 200 - 175
30 - x = 25
x = 30 - 25
x = 5
5) 5( x + 12 ) + 22 = 92
5( x + 12 ) = 92 - 22
5( x + 12 ) = 70
x + 12 = 70 : 5
x + 12 = 14
x = 14 - 12
x = 2
6) 95 - 5( x + 2 ) = 45
5( x + 2 ) = 95 - 45
5( x + 2 ) = 50
x + 2 = 50 : 5
x + 2 = 10
x = 10 - 2
x = 8
7) 14x + 54 = 82
14x = 82 - 54
14x = 28
x = 28 : 14
x = 2
8) 15x - 133 = 17
15x = 17 + 133
15x = 150
x = 150 : 15
x = 10
9) 155 - 10( x + 1 ) = 55
10( x + 1 ) = 155 - 55
10( x + 1 ) = 100
x + 1 = 100 : 10
x + 1 = 10
x = 10 - 1
x = 9