a, (x+1) (x²-x+1) – x(x²-2)=9
b, 2x(x+3) – (x-5) (7+2x)=44
c, (2x+3) (x²+x) – 2x(x²+5x/2=9
d, (x²-3x) (2x-1) – x(2x²-7x)=12
e, (x+2) (x²-4x+1) – ( x³-2x²+2)= -18
a, (x+1) (x²-x+1) – x(x²-2)=9
b, 2x(x+3) – (x-5) (7+2x)=44
c, (2x+3) (x²+x) – 2x(x²+5x/2=9
d, (x²-3x) (2x-1) – x(2x²-7x)=12
e, (x+2) (x²-4x+1) – ( x³-2x²+2)= -18
Đáp án:
`a) x=4`
`b) x=1`
`c) x=3`
`d) x=4`
`e) x=3`
Giải thích các bước giải:
a)
`(x+1)(x^2 -x+1)-x(x^2 -2)=9`
`<=> x^3 + 1 – x^3 + 2x=9`
`<=> 2x=8`
`<=> x=4`
b)
`2x(x+3)-(x-5)(7+2x)=44`
`<=> 2x^2 + 6x – (7x +2x^2 -35 -10x)=44`
`<=> 2x^2 + 6x – 7x – 2x^2 + 35 + 10x = 44`
`<=> 9x + 35 = 44`
`<=> 9x = 9`
`<=> x=1`
c)
`(2x+3)(x^2 + x)- 2x(x^2 + (5x)/2)=9`
`<=> 2x^3 + 2x^2 + 3x^2 + 3x – 2x^3 – 5x^2 =9`
`<=> 3x = 9`
`<=> x=3`
d)
`(x^2 – 3x)(2x – 1) – x(2x^2 – 7x) = 12`
`<=> 2x^3 – x^2 – 6x^2 + 3x – 2x^3 + 7x^2 = 12`
`<=> 3x = 12`
`<=> x=4`
e)
`(x + 2)(x^2 – 4x +1) – (x^3 – 2x^2 + 2)= -18`
`<=> x^3 – 4x^2 + x +2x^2 – 8x + 2 – x^3 +2x^2 -2 = -18`
`<=> -6x = -18`
`<=> x=3`