a, \(=16,24\left(12-3+1\right)\)

\(=16,24.10=162,4\)

b, \(=1,25\left(1+2+7\right)\)

\(=1,25.10=12,5\)

c, \(=2,46\left(2+8\right)\)

\(=2,46.10=24,6\)

\(a,=16,24\times12-16,24\times3+16,24\times1\\ =16,24\times\left(12-3+1\right)=16,24\times10=162,4\\ b,=1,25\times\left(1+2+7\right)=1,25\times10=12,5\)

a 16.24( 12-10+3)=16.24 x 5=81.2

b  1.25(1+2+7)=1.25 x 10= 12.5

c  2.46 x 2 + 2.46 x8 = 2.46(2 + 8)=2.46 x 10=24.6

=(7+2)x1,45+2,45

=14,5

5,62 x 12 – 2 x 0,562 x 10

=(12-2)x5,62

=56,2

42,35 x 15 – 4,235 x 10 x 6 + 42,35

=(15-6)42,35+42,35

=423.5

1)\(y\times7:5+4\times8=134\)

  \(\Leftrightarrow y\times7:5+32=134\)

  \(\Leftrightarrow y\times7:5=102\)

  \(\Leftrightarrow y\times7=510\)

  \(\Leftrightarrow y=72,86\)

2) \(\dfrac{1}{4}:0,25-\dfrac{1}{8}:0,125+\dfrac{1}{2}:0,5-\dfrac{1}{10}\)

\(=0,25:0,25-0,125:0,125+0,5:0,5-\dfrac{1}{10}\)

\(=1-1+1-\dfrac{1}{10}\)

\(=\dfrac{9}{10}\)

\(\left(\frac{7}{2}+2x\right).\frac{8}{3}=\frac{16}{3}\)

 \(\frac{7}{2}+2x=\frac{16}{3}:\frac{8}{3}\)

 \(\frac{7}{2}+2x=2\)

 \(2x=2-\frac{7}{2}\)

\(2x=\frac{-3}{2}\)

\(x=\frac{-3}{2}:2\)

\(x=\frac{-3}{4}\)

\(\frac{1}{3}.x+0,5x=0,75\)

\(\frac{1}{3}x+\frac{1}{2}x=\frac{3}{4}\)

\(x.\left(\frac{1}{3}+\frac{1}{2}\right)=\frac{3}{4}\)

\(x.\frac{5}{6}=\frac{3}{4}\)

\(x=\frac{3}{4}:\frac{5}{6}\)

\(x=\frac{9}{10}\)

Ta có 3(x-3)(x+7)+(x-4)²+48=(3x-9)(x+7)+ (x²-8x+16)+48

                                        = 3x²+21x-9x-63+x²-8x+16+48

                                        = 4x²+4x+1

                                        =(2x+1)²

 ^{Thay x vào rồi tính...  . Ở đây đề là 48 ko phải 47}

may tinh dau!loi ra mau

a) 6x(5x + 3) + 3x(1 – 10x) = 7  

⇒ 30x²+18x+3x-30x²=7

⇒21x=7

⇒x=\(\dfrac{7}{21}\)

⇒x= \(\dfrac{1}{3}\)

b) (3x – 3)(5 – 21x) + (7x + 4)(9x – 5) = 44

⇒15x-63x²-15+63x + 63x²-35x+36x-20=44

⇒79x-35=44

⇒79x=44+35

⇒79x=79

⇒x=1

d) 5x(12x + 7) – 3x(20x – 5) = - 100

⇒60x²+35x-60x²+15=-100

⇒35x+15=-100

⇒35x=-100-15

⇒35x=-115

⇒x=\(\dfrac{-115}{35}\)

⇒x=\(\dfrac{-23}{7}\)