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9.4 the Quadratic Formula. Earlier we looked at how to solve quadratic equations in the form of ax 2 + c = 0 by taking the square root. We are going to look at how to solve ANY quadratic equation in standard form of ax 2 + bx + c = 0
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9.4 the Quadratic Formula • Earlier we looked at how to solve quadratic equations in the form of ax2 + c = 0 by taking the square root. • We are going to look at how to solve ANY quadratic equation in standard form of ax2 + bx + c = 0 • To do this, we use the QUADRATIC FORMULA. No one knows who discovered it, but versions of it go back as far as 2000 B.C. in Babylonia (4,000 yrs. ago)
QUADRATIC FORMULA. • To use the quadratic formula, your equation must be in standard form. • Tells you what the x-intercepts of the equation are. • With a quadratic equation, you may have 2 x-intercepts, 1, or none. (see graphs) X = -b +- b2 – 4ac 2a
Using the quadratic equation • Coefficient of x2 is the “a”, coefficient of x is the “b”, and what’s being added is the “c” • Solve using the quadratic formula X2 + 5x – 14 = 0 X = 2 & -7
To graph a quadratic equation • Find the vertex • Use the quadratic formula to find the x-intercepts. • If there are no x-intercepts, choose an x-value to the right & to the left of the vertex & solve for y
graph Find the vertex & use the quadratic formula to find the x-intercepts X2 + 8x + 12 = 0 -x2 + 4 = 0