76.(-42)+76.(-14)+24.(-56)
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a) 3x + 27 = 9
3x = 9 -27
3x = -18
x = - 18/3
x =- 6
Vậy x= ....
b) 2x + 12 = 3(x - 7 )
2x + 12 = 3x- 21
2x - 3x = -21 -12
-x = -33
=> x = 33
Vậy x =....
c) 2x2 - 1 = 49
2x2 = 49 + 1
2x2 = 50
x2 = 50 /2
x2 = 25
x2 = 52
=> x= 5
Vậy x= ....
bai toan kiem tra15 phut truong minh do. the nao co kho ko giup to voi cac ban
\(4n+1⋮\left(n-3\right)\)
\(\Rightarrow4.\left(n-3\right)+13⋮\left(n-3\right)\)
\(\Rightarrow13⋮\left(n-3\right)\Rightarrow\left(n-3\right)\inƯ\left(13\right)=\left\{\pm1;\pm13\right\}\)
\(\Rightarrow n\in\left\{4;2;16;-10\right\}\)
a)
ƯCLN (a, b) = 9 => a = 9p ; b = 9q (q > p > 0,UCLN(p,q) = 1)
Ta có: a + b = 72
=> 9p + 9q = 72
=> 9.(p + q) = 72
=> p + q = 8 = 1 + 7 = 2 + 6 = 3 + 5 = 4 + 4
Mà q > p
=> \(\left(p;q\right)\in\left\{\left(1;7\right),\left(2;6\right);\left(3,5\right)\right\}\)
\(\Rightarrow\left(a;b\right)\in\left\{\left(9;63\right),\left(18;54\right),\left(27;45\right)\right\}\)
b)
ƯCLN (a, b) = 2 => a = 2m; b = 2n ( m > n > 0; UCLN(m;n) = 1)
Ta có: a.b = 252
=> 2m.2n = 252
=> 4mn = 252
=> m.n = 63 = 1.63 = 3.21 = 7.9
Mà m < n
\(\Rightarrow\left(m;n\right)\in\left\{\left(1;63\right),\left(3,21\right),\left(7,9\right)\right\}\)
\(\Rightarrow\left(a;b\right)\in\left\{\left(2;126\right),\left(6;42\right),\left(14,18\right)\right\}\)
\(76.\left(-42\right)+76.\left(-14\right)+24.\left(-56\right)\)
\(=76.\left(-42+-14\right)+24.\left(-56\right)\)
\(=76.\left(-56\right)+24.\left(-56\right)\)
\(=\left(76+24\right).-56\)
\(=100.-56\)
\(=-5600\)
\(76\left(-42\right)+76\left(-14\right)+24\left(-56\right)\)
\(=76\left[\left(-42\right)+\left(-14\right)\right]+24\left(-56\right)\)
\(=76.\left(-56\right)+24.\left(-56\right)\)
\(=\left(-56\right)\left(76+24\right)\)
\(=\left(-56\right)100=-5600\)