Bài 1: Tìm x biếta) 9(4x + 3)2 = 16(3x - 5)2b) (x3 - x2)2 - 4x2 + 8x - 4 = 0c) x5 + x4 + x3 + x2 + x + 1 = 0Bài 2: Tìm x biếta) 5x3 - 7x2 - 15x + 21 = 0b) (x - 3)2 = 4x2 - 20x + 25 c) (x - 1)2 - 5 = (x + 2)(x - 2) - x(x - 1)d) (2x - 3)3 - (2x + 3)(4x2 - 1) =...
Đọc tiếp
Bài 1: Tìm x biết
a) 9(4x + 3)2 = 16(3x - 5)2
b) (x3 - x2)2 - 4x2 + 8x - 4 = 0
c) x5 + x4 + x3 + x2 + x + 1 = 0
Bài 2: Tìm x biết
a) 5x3 - 7x2 - 15x + 21 = 0
b) (x - 3)2 = 4x2 - 20x + 25
c) (x - 1)2 - 5 = (x + 2)(x - 2) - x(x - 1)
d) (2x - 3)3 - (2x + 3)(4x2 - 1) = -24
Bài 1:
a) \(9\left(4x+3\right)^2=16\left(3x-5\right)^2\)
\(114x^2+216x+81=114x^2-480x+400\)
\(144x^2+216x=144x^2-480x+400-81\)
\(114x^2+216=114x^2-480x+319\)
\(696x=319\)
\(\Rightarrow x=\frac{11}{24}\)
b) \(\left(x^3-x^2\right)^2-4x^2+8x-4=0\)
\(\left(x-1\right)^2\left(x^2+2\right)\left(x+\sqrt{2}\right)\left(x-\sqrt{2}\right)=0\)
\(\Rightarrow x=1\)
c) \(x^5+x^4+x^3+x^2+x+1=0\)
\(\left(x+1\right)\left(x^2+x+1\right)\left(x^2-x+1\right)=0\)
\(\Rightarrow x=-1\)
Bài 2:
a) \(5x^3-7x^2-15x+21=0\)
\(\left(5x-7\right)\left(x+\sqrt{3}\right)\left(x-\sqrt{3}\right)=0\)
\(\Rightarrow x=\frac{7}{5}\)
b) \(\left(x-3\right)^2=4x^2-20x+25\)
\(x^2-6x+9-25=4x^2-20x+25\)
\(x^2-6x+9=4x^2-20x+25-25\)
\(x^2-6x-16=4x^2-20x\)
\(x^2+14x-16=4x^2-4x^2\)
\(-3x^2+14x-16=0\)
\(\Rightarrow\orbr{\begin{cases}x=2\\x=\frac{8}{3}\end{cases}}\)
c) \(\left(x-1\right)^2-5=\left(x+2\right)\left(x-2\right)-x\left(x-1\right)\)
\(x^2-2x=x-4\)
\(x^2-2x=x-4+4\)
\(x^2-2x=x-x\)
\(x^2-3x=0\)
\(\Rightarrow\orbr{\begin{cases}x=0\\x=3\end{cases}}\)
d) \(\left(2x-3\right)^3-\left(2x+3\right)\left(4x^2-1\right)=-24\)
\(-48x^2+56x-24=-24\)
\(-48x^2+56x=-24+24\)
\(-48x^2+56=0\)
\(\Rightarrow\orbr{\begin{cases}x=0\\x=\frac{7}{6}\end{cases}}\)
mình ko chắc
Bài 1
A, 11/24
B, -1
chúc bn học tốt