Algebra · real student question

Solve the inequality 8g - 6(g + 1) < 4(2g - 9).

Question

Solve for gg:

8g6(g+1)<4(2g9)8g-6(g+1)<4(2g-9)

Step-by-step solution

  1. Distribute on both sides.

    8g6g6<8g368g-6g-6<8g-36

    On the left, 6(g+1)-6(g+1) gives 6g6-6g-6; on the right, 4(2g9)4(2g-9) gives 8g368g-36. Both terms inside each bracket must be multiplied.

  2. Combine like terms on the left.

    8g6g=2g2g6<8g368g-6g=2g\quad\Rightarrow\quad 2g-6<8g-36

  3. Move the gg terms to the larger-coefficient side. Subtracting 2g2g (rather than 8g8g) leaves a positive coefficient:

    6<6g36-6<6g-36

    This choice is what lets us finish without ever multiplying or dividing by a negative — so the inequality sign never has to flip.

  4. Collect the constants. Add 3636 to both sides:

    30<6g30<6g

  5. Divide by the positive 6, then check. Since 6>06>0 the direction is preserved:

    5<g,i.e.g>55<g,\qquad\text{i.e.}\qquad g>5

    Test g=6g=6: left =4842=6=48-42=6, right =4(3)=12=4(3)=12, and 6<126<12 ✓. Test g=5g=5: left =4036=4=40-36=4, right =4(1)=4=4(1)=4, and 4<44<4 is false, so 55 is correctly excluded. The solution set is (5,)(5,\infty).

Answer

g>5,g(5,)g>5,\qquad g\in(5,\infty)

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