ta có: a) (x+2)(x2-2x+4)-(18+x3)
=(x3+4)-(18+x3)
=x3+8-18-x3
=8-18
=-10
b)(x-3)(x+3)-(x+5)(x-1)=(x2-9)-(x2-x+5x-5)
=(x2-9)-(x2+4x-5)
=x2-9-x2-4x+5
=-9-4x+5
=-4-4x
=4(-1-x)
a) (x+2)(x2-2x+4)-(18+x3)=(x3+4)-(18+x3)
=x3+4-18-x3
=4-18
=-14
b)(x-3)(x+3)-(x+5)(x-1)=(x2-9)-(x2-x+5x-5)
=(x2-9)-(x2+4x-5)
=x2-9-x2-4x+5
=-9-4x+5
=-4-4x
=4(-1-x)
* \(\left(x+2\right)\left(x^2-2x+4\right)-\left(18+x^3\right)\)
\(=x^3+2^3-18-x^3\)
\(=8-18=-10\)
* \(\left(x-3\right)\left(x+3\right)-\left(x+5\right)\left(x-1\right)\)
\(=x^2-3^2-\left(x^2-x+5x-5\right)\)
\(=x^2-9-x^2+x-5x+5\)
\(=-4x-4=-4.\left(x+1\right)\)
(Nếu đúng thì k cho mình với nhé nhe!)
làm lại, lúc nãy mình nhầm 1 chút:
a) (x+2)(x2-2x+4)-(18+x3)=(x3+4)-(18+x3)
=x3+8-18-x3
=8-18
=-10
b)(x-3)(x+3)-(x+5)(x-1)=(x2-9)-(x2-x+5x-5)
=(x2-9)-(x2+4x-5)
=x2-9-x2-4x+5
=-9-4x+5
=-4-4x
=4(-1-x)