Question

[phanvocammy]

Tìm x, biết :

a. x + (-5) = -14

b. -x + 7 = -23

c. 112 - x = (-3) x (-15)

d. (x - 15) - 27 = 5 mũ 5 : 5 mũ 3

e. (2x +1) mũ 2 = 81

f. (x-5) mũ 3 = -27

Answer 1

[Mặc Chinh Vũ]

\(a)x+\left(-5\right)=-14\)

\(\Leftrightarrow x=-14-\left(-5\right)\)

\(\Leftrightarrow x=-14+5\)

\(\Leftrightarrow x=-9\)

\(b)-x+7=-23\)

\(\Leftrightarrow-x=-23+ \left(-7\right)\)

\(\Leftrightarrow-x=-30\)

\(\Leftrightarrow x=30\)

\(c)112-x=\left(-3\right).\left(-15\right)\)

\(\Leftrightarrow112-x=45\)

\(\Leftrightarrow x=112-45\)

\(\Leftrightarrow x=67\)

\(d)\left(x-15\right)-27=5^5:5^3\)

\(\Leftrightarrow\left(x-15\right)-27=5^2\)

\(\Leftrightarrow\left(x-15\right)-27=25\)

\(\Leftrightarrow x-15=52\)

\(\Leftrightarrow x=67\)

\(e)\left(2x+1\right)^2=81\)

\(\Leftrightarrow\left(2x+1\right)^2=9^2\)

\(\Leftrightarrow2x+1=9\)

\(\Leftrightarrow2x=8\)

\(\Leftrightarrow x=4\)

\(f)(x-5^3)=-27\)

\(f)(x-5^3)=-9^3\)

\(\Leftrightarrow x-5=-9\)

\(\Leftrightarrow x=-4\)

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