@Holliwood#:
Đáp án:
Bài 2:
a) x.(x²+x-3)
b) y².(5-3x²)
c) x.(-x+x²+2)
d) a.(-4b+3a+5)
Bài 3:
a) x1=$\frac{3-√113}{26}$; x2=$\frac{3+√113}{26}$
b) x=$\frac{-4}{13}$
c) x=$\frac{19}{7}$
d) x=4
Giải thích các bước giải:
Bài 2: Trả lời
a) x.(2x²+x-1)-x.(x²+2)
⇔ x.[2x²+x-1-(x²+2)]
⇔ x.[2x²+x-1-x²-2]
⇔ x.(x²+x-3)
b) 2y²+xy²-y².(x-3+3x²)
⇔ y².[2+x-(x-3+3x²)]
⇔ y².[2+x-x+3-3x²]
⇔ y².(5-3x²)
c) 5x²+3x³+2x.(-x²-3x+1)
⇔ x.[5x+3x²+2.(-x²-3x+1)]
⇔ x.(5x+3x²-2x²-6x+2)
⇔ x.(-x+x²+2)
d) $\frac{1}{2}$ab+$\frac{3}{2}$a.(2a-3b+4)-a
⇔ a.[$\frac{1}{2}$b+$\frac{3}{2}$.(2a-3b+4)-1]
⇔ a.[$\frac{1}{2}$b+3a-$\frac{9}{2}$b+6-1]
⇔ a.(-4a+3a+5)
Bài 3: Trả lời
a) 3.(x²-2x+1)+x.(23x)=7
⇔ 3x²-6x+3+x.23x=7
⇔ 3x²-6x+3+x.23x=7
⇔ 3x²-6x+3+23x²=7
⇔ 26x²-6x+3=7
⇔ 26x²-6x+3-7=0
⇔ 26x²-6x-4=0
⇔ 13x²-3x-2=0
⇔ x=$\frac{-(-3)±√(-3)²-4.13.(-2)}{2.13}$
⇔ x=$\frac{3±√9+104}{26}$
⇔ x=$\frac{3±√113}{26}$
⇔ x= $\left \{ {{x=$\frac{3+√113}{26}$ } \atop {x=$\frac{3-√113}{26}$ }} \right.$
⇔ x1=$\frac{3-√113}{26}$; x2=$\frac{3+√113}{26}$
b) 2x.(x-5)-x.(3+2x)-4=0
⇔ 2x²-10x-3x-2x²-4=0
⇔ -13x-4=0
⇔ -13x=4
⇔ x=$\frac{-4}{13}$
c) 5.(2x-1)-3x.(x+1)+3x²=14
⇔ 10x-5-3x²-3x+3x²=14
⇔ 7x-5=14
⇔ 7x=14-5
⇔ 7x=19
⇔ x=$\frac{19}{7}$
d) 3x.(x-2)+2x.(2-x)=x²-8
⇔ 3x²-6x+4x-2x²=x²-8
⇔ x²-2x=x²-8
⇔ -2x=-8
⇔ x=4
Bn tham khao nhé!!!!!!!!!!!!!!!!!!!!!!!!!!!
Xin ctlhn ạ!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
