Question

1) Tính:

a) (x-2)(x2+3x+4)
b) (x-2)(x-x2+4)
c) (x2-1)(x2+2x)
d) (2x-1)(3x+2)(3-x)
e) (x+3)(x2+3x-5)
f) (xy-2)(x3-2x-6)
g) (5x3-x2+2x-3)(4x2-x+2)

2) tìm x:
a) 3x3-3x=0
b) x2-x+14=0

Answer 1

làm nốt

d) (2x-1)(3x+2)(3-x)

=(6x²+x-2)(3-x)

=-6x³+17x²+5x-6

e) (x+3)(x²+3x-5)

=x³+6x²+4x-15

f) (xy-2)(x³-2x-6)

=x⁴y-2x³-2x²y-6xy+4x+12

g) (5x³-x2+2x-3)(4x²-x+2)

=20x⁵-9x⁴+19x³-16x²+7x-6

 

Answer 2

Bài 1:

a) (x-2)(x2+3x+4)

=x(5x+4)-2(5x+4)

= 5x²+4x-10x-8

=5x²-6x-8

Answer 3

bài 1: b)

(x-2)(x-x2+4)

=x(x-2x+4)-2(x-2x+4)

=x(-x+4)-2(-x+4)

= -x²+4x+2x-8

= -x²+6x-8

Answer 4

c) (x2-1)(x2+2x)

=2x.4x-1.4x

=8x²-4x

Answer 5

Bài 2L

a)3x3-3x=0

<=>27-3x=0

=> 3x=0

=>x=0

b) x2-x+14=0

<=>x+14=0

=>x=-14