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Bài 2:
a: \(A=\left(x+1\right)^3+5=20^3+5=8005\)
b: \(B=\left(x-1\right)^3+1=10^3+1=1001\)
1: \(=6x^2+2x-15x-5-x^2+6x-9+4x^2+20x+25-27x^3-27x^2-9x-1\)
=-27x^3-18x^2+4x+10
2: =4x^2-1-6x^2-9x+4x+6-x^3+3x^2-3x+1+8x^3+36x^2+54x+27
=7x^3+37x^2+46x+33
5:
\(=25x^2-1-x^3-27-4x^2-16x-16-9x^2+24x-16+\left(2x-5\right)^3\)
\(=8x^3-60x^2+150-125+12x^2-x^3+8x-60\)
=7x^3-48x^2+8x-35
Giải như sau.
(1)+(2)⇔x2−2x+1+√x2−2x+5=y2+√y2+4⇔(x2−2x+5)+√x2−2x+5=y2+4+√y2+4⇔√y2+4=√x2−2x+5⇒x=3y(1)+(2)⇔x2−2x+1+x2−2x+5=y2+y2+4⇔(x2−2x+5)+x2−2x+5=y2+4+y2+4⇔y2+4=x2−2x+5⇒x=3y
⇔√y2+4=√x2−2x+5⇔y2+4=x2−2x+5, chỗ này do hàm số f(x)=t2+tf(x)=t2+t đồng biến ∀t≥0∀t≥0
Công việc còn lại là của bạn !
\(\left(x+6\right)\left(2x+1\right)=0\)
<=> \(\orbr{\begin{cases}x+6=0\\2x+1=0\end{cases}}\)
<=> \(\orbr{\begin{cases}x=-6\\x=-\frac{1}{2}\end{cases}}\)
Vậy....
hk tốt
^^
a) ( x - 3 )( x + 3 )( x + 2 ) - ( x - 1 )( x2 - 3 ) - 5x( x + 4 )2 - ( x - 5 )2
= ( x2 - 32 )( x + 2 ) - ( x3 - x2 - 3x + 3 ) - 5x( x2 + 8x + 16 ) - ( x2 - 10x + 25 )
= x3 + 2x2 - 9x - 18 - x3 + x2 + 3x - 3 - 5x3 - 40x2 - 80x - x2 + 10x - 25
= ( x3 - x3 - 5x3 ) + ( 2x2 + x2 - 40x2 - x2 ) + ( -9x + 3x + 10x - 80x ) + ( -18 - 3 - 25 )
= -5x3 - 38x2 - 76x - 46
b) 2x( x - 4 )2 - ( x + 5 )( x - 2 )( x + 2 ) + 2( x + 5 )2 - ( x - 1 )2
= 2x( x2 - 8x + 16 ) - ( x + 5 )( x2 - 4 ) + 2( x2 + 10x + 25 ) - ( x2 - 2x + 1 )
= 2x3 - 16x2 + 32x - ( x3 + 5x2 - 4x - 20 ) + 2x2 + 20x + 50 - x2 + 2x - 1
= 2x3 - 16x2 + 32x - x3 - 5x2 + 4x + 20 + 2x2 + 20x + 50 - x2 + 2x - 1
= ( 2x3 - x3 ) + ( -16x2 - 5x2 + 2x2 - x2 ) + ( 32x + 4x + 20x + 2x ) + ( 20 + 50 - 1 )
= x3 - 20x2 + 58x + 69
c) ( x + 5 )2 - 4x( 2x + 3 )2 - ( 2x - 1 )( x + 3 )( x - 3 )
= x2 + 10x + 25 - 4x( 4x2 + 12x + 9 ) - ( 2x - 1 )( x2 - 9 )
= x2 + 10x + 25 - 16x3 - 48x2 - 36x - ( 2x3 - x2 - 18x + 9 )
= x2 + 10x + 25 - 16x3 - 48x2 - 36x - 2x3 + x2 + 18x - 9
= ( -16x3 - 2x3 ) + ( x2 - 48x2 + x2 ) + ( 10x - 36x + 18x ) + ( 25 - 9 )
= -18x3 - 46x2 - 8x + 16
d) -2x( 3x + 2 )( 3x - 2 ) + 5( x + 2 )2 - ( x - 1 )( 2x + 1 )( 2x - 1 )
= -2x( 9x2 - 4 ) + 5( x2 + 4x + 4 ) - ( x - 1 )( 4x2 - 1 )
= -18x3 + 8x + 5x2 + 20x + 20 - ( 4x3 - 4x2 - x + 1 )
= -18x3 + 8x + 5x2 + 20x + 20 - 4x3 + 4x2 + x - 1
= ( -18x3 - 4x3 ) + ( 5x2 + 4x2 ) + ( 8x + 20x + x ) + ( 20 - 1 )
= -22x3 + 9x2 + 29x + 19