SỐ NGUYÊN
tìm x:
[x-1] = -3 12-3. [x-1] =6 12-3.[x-1]=9 [x-1]=[-17] - [15]
[x-1]=[-2]^3 - [-3]^2 [x-1]=[x-9] [2x-1]=[x-5] [x+3]=[x-9]
Nhanh lên!!!!!!!!!!!Mai mik thi Toán đấy!!!😭😭😭😭😭
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2 câu dễ làm trước, 2 câu còn lại tối đi học về mới làm được..(giờ bận rồi)
a) ĐẶt \(x^2+3x+1=a\)
\(A=a\left(a-4\right)-5=a^2-4a-5=\left(a-5\right)\left(a+1\right)\)
\(=\left(x^2+3x-4\right)\left(x^2+3x+2\right)\)
\(=\left(x-1\right)\left(x+4\right)\left(x+1\right)\left(x+2\right)\)
c)\(C=\left[\left(x+1\right)\left(x+7\right)\right]\left[\left(x+3\right)\left(x+5\right)\right]+15\)
\(=\left(x^2+8x+7\right)\left(x^2+8x+15\right)+15\)
Đặt ẩn phụ: \(t=x^2+8x+7\) rồi làm tiếp đi..
Để anh làm nốt vậy.
\(B=\left(x^2+2x\right)^2-2x^2-4x-3\)
\(B=\left(x^2+2x\right)^2-2\left(x^2+2x\right)+1-4\)
\(B=\left(x^2+2x-1\right)^2-2^2\)
\(B=\left(x^2+2x-3\right)\left(x^2+2x+1\right)\)
\(B=\left(x+3\right)\left(x-1\right)\left(x+1\right)^2\)
___
\(D=x^2-2xy+y^2-7x+7y+12\)
\(D=\left(x-y\right)^2-7\left(x-y\right)+12\)
\(D=\left(x-y\right)^2-3\left(x-y\right)-4\left(x-y\right)+12\)
\(D=\left(x-y\right)\left(x-y-3\right)-4\left(x-y-3\right)\)
\(D=\left(x-y-3\right)\left(x-y-4\right)\)
a: \(\Leftrightarrow\left(4x+12\right)\left(3x-2\right)-\left(3x+3\right)\left(4x-1\right)=-27\)
\(\Leftrightarrow12x^2-8x+36x-24-\left(12x^2-3x+12x-3\right)=-27\)
\(\Leftrightarrow12x^2+28x-24-12x^2-9x+3=-27\)
\(\Leftrightarrow19x-21=-27\)
=>19x=-6
hay x=-6/19
b: \(\left(x+1\right)\left(3x^2-x+1\right)+x^2\left(4-3x\right)=\dfrac{5}{2}\)
\(\Leftrightarrow3x^3-x^2+x+3x^2-x+1+4x^2-3x^3=\dfrac{5}{2}\)
\(\Leftrightarrow6x^2+1=\dfrac{5}{2}\)
\(\Leftrightarrow6x^2=\dfrac{3}{2}\)
\(\Leftrightarrow x^2=\dfrac{3}{12}=\dfrac{1}{4}\)
=>x=1/2 hoặc x=-1/2
c: \(\Leftrightarrow2\left(x^2-4\right)-4\left(x^2-x-2\right)+\left(5x+8\right)\left(x+2\right)=0\)
\(\Leftrightarrow2x^2-8-4x^2+4x+8+5x^2+10x+8x+16=0\)
\(\Leftrightarrow3x^2+22x+16=0\)
\(\text{Δ}=22^2-4\cdot3\cdot16=292>0\)
Do đó: Phương trình có hai nghiệm phân biệt là:
\(\left\{{}\begin{matrix}x_1=\dfrac{-22-2\sqrt{73}}{6}=\dfrac{-11-\sqrt{73}}{3}\\x_2=\dfrac{-11+\sqrt{73}}{3}\end{matrix}\right.\)
d: \(\Leftrightarrow20x^2-16x-1=10x^2-2x+5x-1\)
\(\Leftrightarrow10x^2-19x=0\)
=>x(10x-19)=0
=>x=0 hoặc x=19/10
a) \(x^3+2x^2-4x+1\)
\(=\left(x^3+3x^2-x\right)-\left(x^2+3x-1\right)\)
\(=x\left(x^2+3x-1\right)-\left(x^2+3x-1\right)\)
\(=\left(x-1\right)\left(x^2+3x-1\right)\)
c) cho da thuc P(x) =2x^4-7x^3 -2x^2 +13x +6? | Yahoo Hỏi & Đáp
Tham khảo
a) \(\left(x+5\right)^3=64\)
\(\Leftrightarrow\left(x+5\right)^3=4^3\)
\(\Leftrightarrow x+5=4\)
\(\Leftrightarrow x=-1\)
Vậy x = - 1
b) \(x:\left(-\frac{3}{5}\right)^2=-\frac{3}{5}\)
\(\Leftrightarrow x=\left(-\frac{3}{5}\right)^2.\left(-\frac{3}{5}\right)\)
\(\Leftrightarrow x=\left(-\frac{3}{5}\right)^3\)
\(\Leftrightarrow x=-0,216\)
Vậy x = - 0, 216
c) \(\left(\frac{4}{7}\right)^4.x=\left(\frac{4}{7}\right)^6\)
\(\Leftrightarrow x=\left(\frac{4}{7}\right)^6:\left(\frac{4}{7}\right)^4\)
\(\Leftrightarrow x=\left(\frac{4}{7}\right)^2\)
\(\Leftrightarrow\text{x}=\frac{16}{49}\)
Vậy x = 16/49
d) \(\left(-\frac{1}{3}\right)^3x=\frac{1}{81}\)
\(\Leftrightarrow-\frac{1}{27}x=\frac{1}{81}\)
\(\Leftrightarrow x=\frac{1}{81}:\left(-\frac{1}{27}\right)\)
\(\Leftrightarrow x=-\frac{1}{3}\)
Vậy x = - 1/3
a, 15/x - 1/3 = 28/57
15/x = 28/57 + 1/3
15/x = 28/57 + 19/57
15/x = 47/57
x . 47 = 15 . 57
x = 855/47
b, x/2 - 2/5 = 1/10
x/2 = 1/10 + 2/5
x/2 = 1/10 + 4/10
x/2 = 5/10 = 1/2
x/2 = 1/2
=> x=1
a)
5.(12-x)-20=30
⇒60-5x-20=30
⇒-5x=30+20-60
⇒-5x=-10
⇒x=2
b)(17x - 25 ) : 8 + 65 = 92
(17x - 25 ) : 8 + 65 = 81
17x - 25 = 16 x 8 = 128
17x = 128+25=153
x= 153:17 =9
c)
x=23
Giải thích các bước giải:
3x – 10 = 2x + 13
3x-2x=13+10
x=23
d)4(2x+7)-3(3x-2)=24
4.2x+4.7-3.3x+3.2=24
8x+28-9x+6=24
8x-9x=24-28-6=-10
=>(-1)x=-10
x=-10:(-1)
x=10
a. \(5\cdot\left(12-x\right)-20=30\Leftrightarrow5\left(12-x\right)=50\)
\(\Leftrightarrow12-x=50:5=10\)
\(\Leftrightarrow x=12-10=2\)
b. \(\left(17x-25\right):8+65=9^2\)
\(\Leftrightarrow\left(17x-25\right):8=81-65=16\)
\(\Leftrightarrow17x-25=16:8=2\)
\(\Leftrightarrow17x=2+25=27\Leftrightarrow x=\frac{27}{17}\)
c. \(3x-10=2x+13\)
\(\Leftrightarrow3x-2x=10+13\)
\(\Leftrightarrow x=23\)
d. \(4\cdot\left(2x+7\right)-3\cdot\left(3x-2\right)=24\)
\(\Leftrightarrow8x+28-9x+6=24\)
\(\Leftrightarrow34-x=24\Leftrightarrow x=10\)
mik chưa học dến số nguyên