Solve the Quadratic: Finding x in 4x² = 12x - 9

Question

4x2=12x9 4x^2=12x-9

Video Solution

Solution Steps

00:00 Find X
00:03 Arrange the equation so that one side equals 0
00:14 Break down 4 into 2 squared
00:21 Break down 9 into 3 squared
00:26 Break down 12 into factors 2,2 and 3
00:33 Use the shortened multiplication formulas to find the brackets
00:41 Isolate X
00:55 And this is the solution to the question

Step-by-Step Solution

To solve the quadratic equation 4x2=12x9 4x^2 = 12x - 9 , we begin by rewriting it in standard quadratic form:

4x212x+9=04x^2 - 12x + 9 = 0

Here, we compare to the general form ax2+bx+c=0 ax^2 + bx + c = 0 and identify:

  • a=4a = 4
  • b=12b = -12
  • c=9c = 9

We will now use the quadratic formula:

x=b±b24ac2ax = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}

Substitute in the values for aa, bb, and cc:

x=(12)±(12)244924x = \frac{-(-12) \pm \sqrt{(-12)^2 - 4 \cdot 4 \cdot 9}}{2 \cdot 4}

Simplify:

x=12±1441448x = \frac{12 \pm \sqrt{144 - 144}}{8}

x=12±08x = \frac{12 \pm \sqrt{0}}{8}

x=12±08x = \frac{12 \pm 0}{8}

This simplifies further to:

x=128=32x = \frac{12}{8} = \frac{3}{2}

Therefore, the solution to the equation 4x2=12x9 4x^2 = 12x - 9 is x=32 x = \frac{3}{2} .

Answer

x=32 x=\frac{3}{2}