Toán rút gọn (x-2).(x^2 +2x +4)-6x^2+12 và (2x +5).(5-2x)+(x-5).(5+4x) 06/07/2021 By Valentina rút gọn (x-2).(x^2 +2x +4)-6x^2+12 và (2x +5).(5-2x)+(x-5).(5+4x)
Đáp án + Giải thích các bước giải: `(x-2)(x^2+2x+4)-6x^2+12` `=x^3-8-6x^2+12` `=x^3-6x^2+4` `(2x+5)(5-2x)+(x-5)(5+4x)` `= 10x – 4x^2+25-10x+5x+4x^2-25-20x` `= (10x-10x-20x+5x)+(-4x^2+4x^2)+(25-25)` `= -15x` Trả lời
a, (x-2)(x²+2x+4)-6x²+12 =x(x²+2x+4)−2(x²+2x+4)−6x²+12 =x³+2x²+4x−2x²−4x−8−6x²+12 =x³−8−6x²+12 =x³−6x²+4 b, (2x+5)(5−2x)+(x−5)(5+4x) =(2x+5)(−2x+5)+(x−5)(5+4x) =2x(−2x+5)+5(−2x+5)+(x−5)(5+4x) =−4x²+10x+5(−2x+5)+(x−5)(5+4x) =−4x²+10x−10x+25+(x−5)(5+4x) =−4x²+25+(x−5)(4x+5) =−4x²+25+x(4x+5)−5(4x+5) =−4x²+25+4x²+5x−20x−25 =−15x Trả lời
Đáp án + Giải thích các bước giải:
`(x-2)(x^2+2x+4)-6x^2+12`
`=x^3-8-6x^2+12`
`=x^3-6x^2+4`
`(2x+5)(5-2x)+(x-5)(5+4x)`
`= 10x – 4x^2+25-10x+5x+4x^2-25-20x`
`= (10x-10x-20x+5x)+(-4x^2+4x^2)+(25-25)`
`= -15x`
a, (x-2)(x²+2x+4)-6x²+12
=x(x²+2x+4)−2(x²+2x+4)−6x²+12
=x³+2x²+4x−2x²−4x−8−6x²+12
=x³−8−6x²+12
=x³−6x²+4
b, (2x+5)(5−2x)+(x−5)(5+4x)
=(2x+5)(−2x+5)+(x−5)(5+4x)
=2x(−2x+5)+5(−2x+5)+(x−5)(5+4x)
=−4x²+10x+5(−2x+5)+(x−5)(5+4x)
=−4x²+10x−10x+25+(x−5)(5+4x)
=−4x²+25+(x−5)(4x+5)
=−4x²+25+x(4x+5)−5(4x+5)
=−4x²+25+4x²+5x−20x−25
=−15x