Algebra · real student question

Factor 2x^2 + 4x.

Question

Factor

2x2+4x2x^{2}+4x

Step-by-step solution

  1. Build the GCF from the numbers and the variables separately. For the coefficients, gcd(2,4)=2\gcd(2,4)=2. For the variables, x2x^{2} and xx share one factor of xx — always the lowest power present. Multiplying the two parts:

    GCF=2x\text{GCF}=2x

    Taking only 22, or only xx, would leave the job half done.

  2. Divide each term by 2x2x.

    2x22x=x,4x2x=2\frac{2x^{2}}{2x}=x,\qquad\frac{4x}{2x}=2

    so the quotients xx and 22 form the bracket:

    2x2+4x=2x(x+2)2x^{2}+4x=2x(x+2)

  3. Check the bracket is fully reduced. Inside, xx and 22 share no common factor, so nothing more can come out — the factorisation is complete. (By contrast, the partial answer 2(x2+2x)2\left(x^{2}+2x\right) is a true identity but still hides a common xx.)

  4. Verify by expanding. 2xx+2x2=2x2+4x2x\cdot x+2x\cdot2=2x^{2}+4x ✓, confirmed at every integer from 20-20 to 1919 ✓.

  5. Read off the roots. Setting 2x(x+2)=02x(x+2)=0 and applying the zero-product property gives x=0x=0 or x=2x=-2. The constant 22 contributes no root. Both check out: 2(0)+0=02(0)+0=0 ✓ and 2(4)+4(2)=88=02(4)+4(-2)=8-8=0 ✓.

Answer

2x2+4x=2x(x+2)2x^{2}+4x=2x(x+2)

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