Bài 1 : Phân tích đa thức thành nhân tử :
a) X^2 – 5x +6 b ) 3x^2 + 9x – 30 c) x^2 – 3x + 2
d)X^2 – 9x + 18 e) x^2 -6x + 8 f) x^2 -5x -14
g) x^2 + 6x +5 h) x^2 – 7x +12 i) x^2 – 7x+ 10
Bài 2 :
a) 3x^2 – 5x 2
b) 2x^2 + x -6
c) 7x^2 + 50x +7
d) 12x^2 +7 – 12
e) 15x^2 + 7x-2
f) A^2 -5a – 14
g) 2m^2 + 10m + 8
h) 4p^2 – 36p + 56
i) 2x^2 + 5x + 2
Bài 1: a) x2 - 5x + 6 = x2 - 2x - 3x + 6 = x(x - 2) - 3(x - 2) = (x - 3)(x - 2)
b) 3x2 + 9x - 30 = 3x2 + 15x - 6x - 30 = 3x(x + 5) - 6(x + 5) = (3x - 6)(x + 5) = 2(x - 2)(x + 5)
c) x2 - 3x + 2 = x2 - 2x - x + 2 = x(x - 2) - (x - 2) = (x - 1)(x - 2)
d) x2 - 9x + 18 = x2 - 3x - 6x + 18 = x(x - 3) - 6(x - 3) = (x - 6)(x - 3)
e) x2 - 6x + 8 = x2 - 2x - 4x + 8 = x(x - 2) - 4(x - 2) = (x - 4)(x - 2)
f) x2 - 5x - 14 = x2 - 7x + 2x - 14 = x(x - 7) + 2(x - 7) = (x + 2)(x - 7)
g) x2 + 6x + 5 = x2 + 5x + x + 5 = x(x + 5) + (x + 5) = (x + 1)(x + 5)
h) x2 - 7x + 12 = x2 - 3x - 4x + 12 = x(x - 3) - 4(x - 3) = (x - 4)(x - 3)
i) x2 - 7x + 10 = x2 - 2x - 5x + 10 = x(x - 2) - 5(x - 2) = (x - 5)(x - 2)
Oh Sehun:Ít một thôi bạn ơi!Làm xong đống này chắc đến tuổi già mất:(
a
\(x^2-5x+6\)
\(=\left(x^2-3x\right)-\left(2x-6\right)\)
\(=\left(x-3\right)\left(x-2\right)\)
b
\(3x^2+9x-30\)
\(=x^2+3x-10\)
\(=\left(x^2-2x\right)+\left(5x-10\right)\)
\(=\left(x-2\right)\left(x+5\right)\)
c
\(x^2-3x+2\)
\(=\left(x^2-x\right)-\left(2x-2\right)\)
\(=\left(x-1\right)\left(x-2\right)\)
d
\(x^2-9x+18\)
\(=\left(x^2-3x\right)-\left(6x-18\right)\)
\(=\left(x-3\right)\left(x-6\right)\)
e
\(x^2-6x+8\)
\(=\left(x^2-2x\right)-\left(4x-8\right)\)
\(=\left(x-2\right)\left(x-4\right)\)
f
\(x^2-5x-14\)
\(=\left(x^2+2x\right)-\left(7x+14\right)\)
\(=\left(x+2\right)\left(x-7\right)\)
g
\(x^2+6x+5\)
\(=\left(x^2+x\right)+\left(5x+5\right)\)
\(=\left(x+1\right)\left(x+5\right)\)
h
\(x^2-7x+12\)
\(=\left(x^2-3x\right)-\left(4x-12\right)\)
\(=\left(x-3\right)\left(x-4\right)\)
i
\(x^2-7x+10\)
\(=\left(x^2-2x\right)-\left(5x-10\right)\)
\(=\left(x-2\right)\left(x-5\right)\)
P/S:Cho e xin phép tách câu ạ.
Bài 2: a) xlđ
b) 2x2 + x - 6 = 2x2 + 4x - 3x - 6 = 2x(x + 2) - 3(x + 2) = (2x - 3)(x + 2)
c) 7x2 + 50x + 7 = 7x2 + x + 49x + 7 = x(7x + 1) + 7(7x + 1) = (x + 7)(7x + 1)
d) 12x2 + 7x - 12 = 12x2 + 16x - 9x - 12 = 4x(3x + 4) - 3(3x + 4) = (4x - 3)(3x + 4)
e) 15x2 + 7x - 2 = 15x2 + 10x - 3x - 2 =5x(3x + 2) - (3x + 2) = (5x - 1)(3x + 2)
f) a2 - 5a - 14 = a2 - 7a + 2a - 14 = a(a - 7) + 2(a - 7) = (a + 2)(a - 7_
g) 2m2 + 10m + 8 = 2m2 + 2m + 8m + 8 = 2m(m + 1) + 8(m + 1) = (2m + 8)(m + 1) = 2(m + 4)(m + 1)
h) 4p2 - 36p + 56 = 4(p2 - 9p + 14) = 4(p2 - 2p - 7p + 14) = 4[p(p - 2) - 7(p - 2)] = 4(p - 7)(p - 2)
i) 2x2 + 5x + 2 = 2x2 + x + 4x + 2 = x(2x + 1) + 2(2x + 1) = (x + 2)(2x + 1)
Bài 2
a.Ko hiểu đề:V
b.
\(2x^2+x-6\)
\(=\left(2x^2+4x\right)-\left(3x+6\right)\)
\(=\left(x-2\right)\left(2x-3\right)\)
c
\(7x^2+50x+7\)
\(=\left(7x^2+x\right)+\left(49x+7\right)\)
\(=\left(x+7\right)\left(7x+1\right)\)
d
\(12x^2+7x-12\)
\(=\left(12x^2+16x\right)-\left(9x+12\right)\)
\(=\left(3x+4\right)\left(4x-3\right)\)
e
\(15x^2+7x-2\)
\(=\left(15x^2+10x\right)-\left(3x+2\right)\)
\(=\left(3x+2\right)\left(5x-1\right)\)
f
\(a^2-5a-14\)
\(=\left(a^2+2a\right)-\left(7a+14\right)\)
\(=\left(a+2\right)\left(a-7\right)\)
g
\(2m^2+10m+8\)
\(=2\left(m^2+5m+4\right)\)
\(=2\left[\left(m^2+m\right)+\left(4m+4\right)\right]\)
\(=2\left(m+1\right)\left(m+4\right)\)
h
\(4p^2-36p+56\)
\(=4\left(p^2-9p+14\right)\)
\(=4\left[\left(p^2-7p\right)-\left(2p-14\right)\right]\)
\(=4\left(p-7\right)\left(p-2\right)\)
i
\(2x^2+5x+2\)
\(=\left(2x^2+x\right)+\left(4x+2\right)\)
\(=\left(x+2\right)\left(2x+1\right)\)
