Question

[Phạm Đỗ Bảo Ngọc]

bài 5 ; tìm x

f, a mũ 2 + x -x mũ 2 - a = a

g, x mũ 2 + 3x - ( 2x + 6 ) = 0

h, 5x + 20 - x mũ 2 - 4x =0

m, x mũ 3 - 5x mũ 2 - x + 5 = 0

n, x ( x - 3 ) - 7x + 21 = 0

Answer 1

[Nguyễn Huy Tú]

Bài 5 : 

f, bạn xem lại đề hay là tìm x chứa tham số a ? 

g, \(x^2+3x-\left(2x+6\right)=0\Leftrightarrow x\left(x+3\right)-2\left(x+3\right)=0\)

\(\Leftrightarrow\left(x-2\right)\left(x+3\right)=0\Leftrightarrow x=-3;x=2\)

h, \(5x+20-x^2-4x=0\Leftrightarrow5\left(x+4\right)-x\left(x+4\right)=0\)

\(\Leftrightarrow\left(5-x\right)\left(x+4\right)=0\Leftrightarrow x=-4;x=5\)

m, \(x^3-5x^2-x+5=0\Leftrightarrow x^2\left(x-5\right)-\left(x-5\right)=0\)

\(\Leftrightarrow\left(x-1\right)\left(x+1\right)\left(x-5\right)=0\Leftrightarrow x=\pm1;x=5\)

n, \(x\left(x-3\right)-7x+21=0\Leftrightarrow x\left(x-3\right)-7\left(x-3\right)=0\)

\(\Leftrightarrow\left(x-7\right)\left(x-3\right)=0\Leftrightarrow x=3;x=7\)

Answer 2

[Đỗ Minh Châu]

x=7 nha