Question

Tìm số nguyên x biết:

a)-2(2x-8)+3(4-2x)=-72-5(3x-7)

b)3.(2x²-7)=33

Answer 1

b)

\(3\left(2x^2-7\right)=33\)

\(\Leftrightarrow2x^2-7=11\)

\(\Leftrightarrow2x^2=18\)

\(\Leftrightarrow x^2=9\)

\(\Leftrightarrow x=\pm3\)

Answer 2

a) -2(2x - 8) + 3(4 - 2x) = -72 - 5(3x - 7)

=> -4x + 16 + 12 - 6x = -72 - 15x + 35

=> -10x + 28 = -37 - 15x

=> -10x + 15x = -37 - 28

=> 5x = -65

=> x = -65 : 5

=> x = -13

b) 3(2x² - 7) = 33

=> 2x² - 7 = 33 : 3

=> 2x² - 7 = 11

=> 2x² = 11 + 7

=> 2x² = 18

=> x² = 18 : 2

=> x² = 9

=> \(\orbr{\begin{cases}x=3\\x=-3\end{cases}}\)

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