Question

Tìm x biết:

a, 17-(43-|x|)=45

b, (x-2).(x+15)=0

c, 2x^2-3=29

Answer 1

a.\(17-\left(43-\left|x\right|\right)=45\)

\(\Leftrightarrow43-\left|x\right|=17-45\)

\(\Leftrightarrow43-\left|x\right|=-28\)

\(\Leftrightarrow\left|x\right|=43+28\)

\(\Leftrightarrow\left|x\right|=71\)

\(\Leftrightarrow x\in\left\{-71;71\right\}\)

b. \(\left(x-2\right)\left(x+15\right)=0\Leftrightarrow x\in\left\{2;-15\right\}\)

c. \(2x^2-3=29\)

\(\Leftrightarrow2x^2=29+3\)

\(\Leftrightarrow2x^2=32\)

\(\Leftrightarrow x^2=32\div2\)

\(\Leftrightarrow x^2=16\)

\(\Leftrightarrow x^2=4^2=\left(-4\right)^2\)

Vậy x = 4 hoặc x = 4