14 x 5 = 70

Chúc bn hk tốt ^^

14 x 5 = 70

\(9x^2-12xy-20y-25=9x^2-25-4y\left(3x+5\right)\)

\(=\left(3x+5\right)\left(3x-5\right)-4y\left(3x+5\right)=\left(3x+5\right)\left(3x-4y-5\right)\)

\(xy^2-49x^3-28x^2-4x=x\left[y^2-\left(49x^2+28x+4\right)\right]\)

\(=x\left[y^2-\left(7x+2\right)^2\right]=x\left(y+7x+2\right)\left(y-7x-2\right)\)

\(x^2-3x-2019.2022=x^2-3x-2019\left(2019+3\right)\)

\(=x^2-3x-2019^2-3.2019=\left(x-2019\right)\left(x+2019\right)-3\left(x+2019\right)\)

\(=\left(x+2019\right)\left(x-2022\right)\)

a: \(9x^2-12xy-20y-25\)

\(=\left(3x-5\right)\left(3x+5\right)-4y\left(3x+5\right)\)

\(=\left(3x+5\right)\left(3x-5-4y\right)\)

bang no ha ha

 mk đang vội nên giúp bn bt KQ thôi nha

ĐS=-21503

a: Ta có: \(24=2^3\cdot3;36=2^2\cdot3^2;160=2^5\cdot5\)

=>ƯCLN(24;36;160)=2^2=4

24⋮x; 36⋮x; 160⋮x

Do đó: x∈ƯC(24;36;160)

mà x lớn nhất

nên x=ƯCLN(24;36;160)=4

b: \(54=2\cdot3^3;12=2^2\cdot3\)

=>ƯCLN(54;12)=2*3=6

x∈ƯC(54;12)

mà x lớn nhất

nên x=ƯCLN(54;12)

=>x=6

c: \(4=2^2;6=2\cdot3\)

=>BCNN(4;6)=\(2^2\cdot3=12\)

x⋮4; x⋮6

=>x∈BC(4;6)

=>x∈B(12)

mà 0<x<50

nên x∈{12;24;36;48}

d: \(12=2^2\cdot3;18=2\cdot3^2\)

=>BCNN(12;18)=\(2^2\cdot3^2=36\)

x⋮12; x⋮18

=>x∈BC(12;18)

=>x∈B(36)

mà x<250

nên x∈{36;72;108;144;180;216}

e: \(36=2^2\cdot3^2;24=2^3\cdot3\)

=>ƯCLN(36;24)=\(2^2\cdot3=12\)

x∈ƯC(36;24)

=>x∈Ư(12)

mà x<=20

nên x∈{1;2;3;4;6;12}

f: \(91=13\cdot7;26=2\cdot13\)

=>ƯCLN(91;26)=13

91⋮x; 26⋮x

=>x∈ƯC(91;26)

=>x∈Ư(13)

mà 10<x<30

nên x=13

g: 2=2; 3=3; 5=5; 7=7

=>BCNN(2;3;5;7)=\(2\cdot3\cdot5\cdot7=210\)

x⋮2; x⋮3; x⋮5; x⋮7

=>x∈BC(2;3;5;7)

mà x nhỏ nhất

nên x=BCNN(2;3;5;7)

=>x=210

h: \(6=2\cdot3;4=2^2\)

=>BCNN(6;4)=\(2^2\cdot3=12\)

x∈BC(6;4)

=>x∈B(12)

mà 16<=x<=50

nên x∈{24;36;48}

Câu 1: 4¹⁴ . 5²⁸ = 4¹⁴ . (5²)¹⁴ = 4¹⁴ . 25¹⁴ = (4.25)¹⁴ = 100¹⁴

Câu 2: 12⁸ . 2¹⁶ = 12⁸ . (2²)⁸ = 12⁸ . 4⁸ = (12.4)⁸ = 48⁸

Có: 4x⁴+36x²+81=(2x²+9)²

<=>4x⁴+36x²+81-36x²=(2x²+9)²-36x²