Solve the inequalities
−3≤4−7x2≤18
We have,
−3≤4−7x2≤18
Add −4 on each of the sides, we get
−3−4≤−4+4−7x2≤18−4
⇒−7≤−7x2≤14
Multiply 27 on each of the sides
⇒−2≤−x≤4
Now multiply each side by −1
⇒2≥x≥−4, since after multiplying any inequalty by negative number its sign reverses
⇒−4≤x≤2
⇒x∈[−4,2]