a) (-12)(x - 5) + 7.(3 - x) = 5
(-12)x - (-60) + 21 - 7x = 5
(-12)x - 7x + 60 + 21 = 5
(-19)x + 81 = 5
(-19)x = -76
x = (-76)/(-19) = 4
a) \(-12\cdot\left(x-5\right)+7\cdot\left(x-3\right)=5\)
\(\Leftrightarrow-12x+60+21-7x=5\)
\(\Leftrightarrow-19x+81=5\)
\(\Leftrightarrow-19x=5-81\)
\(\Leftrightarrow-19x=-76\)
\(\Leftrightarrow x=\frac{\left(-76\right)}{\left(-19\right)}\)
\(\Leftrightarrow x=4\)
a) \(-12.\left(x-5\right)+7.\left(3-x\right)=5\)
\(-12x+60+21-7x=5\)
\(-19x+81=5\)
\(-19x=5-81\)
\(-19x=-76\)
\(x=4\)
-12.(x-5)+7.(3-x)=5
-12.x+60+21-7x=5
-12.x+81-7x =5
(-12-7).x =5-81
-19.x =-76
x =-76:(-19)
x = 4
b) 30 ( x + 2) -6 ( x -5 ) -24x = 100
<=> 30x + 60 -6x + 30 - 24x -100 = 0
<=> 0x -10 = 0
<=> x = \(\varphi\)
Vậy....
b, 30.(x+2)-6.(x-5).24x=100
30x+60-6x-30.24x=100
30x-6x+60-30.24x=100
24x+30.24x=100
x.(24.24)+30=100
576x+30=100
576x =70
x = 70/576
x=35/288
b) 30 ( x + 2) -6 ( x -5 ) -24x = 100
<=> 30x + 60 -6x + 30 - 24x -100 = 0
<=> 0x -10 = 0
<=> x = $\varphi$φ
Vậy....
b) 30 ( x + 2) -6 ( x -5 ) -24x = 100
<=> 30x + 60 -6x + 30 - 24x -100 = 0
<=> 0x -10 = 0
<=> x = $$
Vậy....
bÀI LÀM
a) x4+x3+2x2+x+1=(x4+x3+x2)+(x2+x+1)=x2(x2+x+1)+(x2+x+1)=(x2+x+1)(x2+1)
b)a3+b3+c3-3abc=a3+3ab(a+b)+b3+c3 -(3ab(a+b)+3abc)=(a+b)3+c3-3ab(a+b+c)
=(a+b+c)((a+b)2-(a+b)c+c2)-3ab(a+b+c)=(a+b+c)(a2+2ab+b2-ac-ab+c2-3ab)=(a+b+c)(a2+b2+c2-ab-ac-bc)
c)Đặt x-y=a;y-z=b;z-x=c
a+b+c=x-y-z+z-x=o
đưa về như bài b
d)nhóm 2 hạng tử đầu lại và 2hangj tử sau lại để 2 hạng tử sau ở trong ngoặc sau đó áp dụng hằng đẳng thức dề tính sau đó dặt nhân tử chung
e)x2(y-z)+y2(z-x)+z2(x-y)=x2(y-z)-y2((y-z)+(x-y))+z2(x-y)
=x2(y-z)-y2(y-z)-y2(x-y)+z2(x-y)=(y-z)(x2-y2)-(x-y)(y2-z2)=(y-z)(x2-2y2+xy+xz+yz)
a) (-12)(x - 5) + 7.(3 - x) = 5
(-12)x - (-60) + 21 - 7x = 5
(-12)x - 7x + 60 + 21 = 5
(-19)x + 81 = 5
(-19)x = -76
x = \(\frac{-76}{-19}\) = 4
b)
b) 30 ( x + 2) -6 ( x -5 ) -24x = 100
<=> 30x + 60 -6x + 30 - 24x -100 = 0
<=> 0x -10 = 0
<=>\(x\in\varnothing\)
Vậy....
-12.(x-5) + 7.(3-x) = 5
-12x + 60 + 21 - 7x = 5
-19x + 81 = 5
-19x = -76
x = \(\frac{-76}{-19}\)
x = 4
a) (-12)(x - 5) + 7.(3 - x) = 5
(-12)x - (-60) + 21 - 7x = 5
(-12)x - 7x + 60 + 21 = 5
(-19)x + 81 = 5
(-19)x = -76
x = (-76)/(-19) = 4
b) 30 ( x + 2) -6 ( x -5 ) -24x = 100
<=> 30x + 60 -6x + 30 - 24x -100 = 0
<=> 0x -10 = 0
<=> x = \(\varnothing\)
a, -12(x - 5) + 7(3 - x) = 5
-12x + 60 + 21 - 7x = 5
-19x + 81= 5
-19x = -76
x = 4
b, 30(x + 2) - 6(x - 5) - 24x = 100
30x + 60 - ( 6x - 30) - 24x = 100
0x + 90 = 100
0x = 10
x = O
\(a,-12.\left(x-5\right)+7.\left(3-x\right)=5\)
\(=>-12x+60+21-7x=5\)
\(=>-19x=5-84=-76\)
\(=>x=\frac{-76}{-19}=4\)
\(b,30.\left(x+2\right)-6.\left(x-5\right).24x=100\)
\(=>30x+60-6x+30.24x=100\)
\(=>30x-6x+60+720x=100\)
\(=>720x+24x=100-60=40\)
\(=>744x=40=>x=\frac{40}{744}=\frac{5}{93}\)
\(a,-12\left(x-5\right)+7\left(3-x\right)=5\)
\(-12x+60+21-7x=5\)
\(-19x+81=5\)
\(-19x=-76\Leftrightarrow x=4\)
Tương tự cách thực hiện vs phần b
