Algebra · real student question

Solve the equation 2x^2 - 5x + 3 = 0.

Question

Solve

2x25x+3=02x^2-5x+3=0

Step-by-step solution

  1. Use the AC method because the leading coefficient is not 11. Multiply aa by cc:

    ac=23=6a\cdot c=2\cdot 3=6

    and look for two numbers with product 66 and sum b=5b=-5. They are 2-2 and 3-3.

  2. Split the middle term with that pair.

    2x22x3x+3=02x^2-2x-3x+3=0

    The split is legitimate because 2x3x=5x-2x-3x=-5x, so nothing has changed.

  3. Group in pairs and factor each group.

    2x(x1)3(x1)=02x(x-1)-3(x-1)=0

    Both groups now share the binomial (x1)(x-1), which confirms the split was the right one.

  4. Factor out the common binomial and solve.

    (2x3)(x1)=0x=32 or x=1(2x-3)(x-1)=0\quad\Longrightarrow\quad x=\frac{3}{2}\ \text{or}\ x=1

  5. Check both roots. At x=1x=1: 25+3=02-5+3=0 \checkmark. At x=32x=\tfrac32: 2(94)152+3=92152+3=02\left(\tfrac94\right)-\tfrac{15}{2}+3=\tfrac92-\tfrac{15}{2}+3=0 \checkmark. Vieta agrees: the roots sum to 52=ba\tfrac52=-\tfrac{b}{a} and multiply to 32=ca\tfrac32=\tfrac{c}{a}.

Answer

x=1orx=32x=1\quad\text{or}\quad x=\frac{3}{2}

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