Algebra · real student question

Solve the equation negative 4 times (negative 11 plus 5x) plus 6 times (26 minus 6x) equals negative 3 times (4x plus 1) plus 5 times (11 plus 6x).

Question

Solve for xx:

4(11+5x)+6(266x)=3(4x+1)+5(11+6x)-4(-11+5x)+6(26-6x)=-3(4x+1)+5(11+6x)

Step-by-step solution

  1. Expand the left-hand side, tracking every sign. A negative multiplier in front of a bracket that already contains a negative is the classic place to slip:

    4(11+5x)=4420x-4(-11+5x)=44-20x

    6(266x)=15636x6(26-6x)=156-36x

    Adding them:

    LHS=4420x+15636x=20056x\text{LHS}=44-20x+156-36x=200-56x

  2. Expand the right-hand side the same way.

    3(4x+1)=12x3-3(4x+1)=-12x-3

    5(11+6x)=55+30x5(11+6x)=55+30x

    Adding them, and combining 12x-12x with +30x+30x:

    RHS=12x3+55+30x=18x+52\text{RHS}=-12x-3+55+30x=18x+52

    It is worth pausing here: 12+30=18-12+30=18, not 2222. Mis-adding these two coefficients is the single most common error in this problem.

  3. Write the simplified equation.

    20056x=18x+52200-56x=18x+52

  4. Gather like terms. Add 56x56x to both sides and subtract 5252 from both sides:

    20052=18x+56x200-52=18x+56x

    148=74x148=74x

  5. Divide and simplify.

    x=14874=2x=\frac{148}{74}=2

  6. Substitute x=2x=2 into the original equation. Left side:

    4(11+10)+6(2612)=4(1)+6(14)=4+84=88-4(-11+10)+6(26-12)=-4(-1)+6(14)=4+84=88

    Right side:

    3(8+1)+5(11+12)=27+115=88-3(8+1)+5(11+12)=-27+115=88

    Both sides are 8888, so x=2x=2 is confirmed. The equation does have a solution — the no solution option offered on this exercise is a distractor.

Answer

x=2x=2

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