Algebra · real student question

Solve the negative of (5x - 4), plus 2 times (x - 7), equals -1.

Question

Solve for xx:

(5x4)+2(x7)=1-(5x-4)+2(x-7)=-1

Step-by-step solution

  1. Read the leading minus as multiplication by 1-1. It applies to both terms inside the bracket:

    (5x4)=5x+4-(5x-4)=-5x+4

    The constant becomes +4+4. Writing 5x4-5x-4 here is the most frequent error in this type of equation.

  2. Distribute the 2 over the second bracket.

    2(x7)=2x142(x-7)=2x-14

    so the equation reads

    5x+4+2x14=1-5x+4+2x-14=-1

  3. Combine like terms.

    5x+2x=3x,414=103x10=1-5x+2x=-3x,\qquad 4-14=-10\quad\Rightarrow\quad -3x-10=-1

  4. Isolate the xx term. Add 1010 to both sides:

    3x=9-3x=9

  5. Divide by the negative coefficient and check.

    x=93=3x=\frac{9}{-3}=-3

    Substituting back: (5(3)4)+2(37)=(19)+2(10)=1920=1-(5(-3)-4)+2(-3-7)=-(-19)+2(-10)=19-20=-1 ✓. (This is an equation, so dividing by 3-3 needs no sign flip — that rule belongs to inequalities.)

Answer

x=3x=-3

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