Practice Quadratic Formula in Math

Use these practice problems to test your method after reviewing the concept explanation and worked examples.

Quick Recap

A formula giving the exact solutions to any quadratic equation ax2+bx+c=0 directly from its three coefficients.

When factoring fails, this formula always finds the x-intercepts.

Showing a random 20 of 50 problems.

Example 1

medium
Solve 5x2−2x−3=0.

Example 2

easy
Solve x2−4x+4=0.

Example 3

medium
Solve x2−4x+1=0. Leave answers in exact form.

Example 4

medium
Solve x2−6x+13=0.

Example 5

challenge
If the roots of x2−8x+k=0 are in the ratio 3:1, find k.

Example 6

medium
Solve x+6x=5.

Example 7

challenge
Find all values of a for which x2+ax+4=0 has two distinct positive real roots.

Example 8

easy
Solve x2+2x−8=0.

Example 9

medium
A rectangular garden has area 54 m² and its length is 3 m more than its width. Find the width.

Example 10

easy
Find the discriminant of 5x2−3x+1=0 and state how many real roots the equation has.

Example 11

medium
Solve 2x2+x−6=0.

Example 12

challenge
Prove that for any real a, the equation x2+ax+(a−1)=0 has at least one real solution.

Example 13

easy
Solve 2x2−4x−6=0.

Example 14

medium
Solve 3x2−4x−4=0 using the quadratic formula.

Example 15

hard
A projectile follows h(t)=−5t2+25t+1 metres. When does it reach height 20 m? Give all solutions to two decimal places.

Example 16

hard
Find values of k such that x2+(k+2)x+9=0 has no real roots.

Example 17

easy
Solve x2−5x+6=0 using the quadratic formula.

Example 18

medium
Solve x2+5x−14=0.

Example 19

hard
Solve x4−10x2+9=0.

Example 20

medium
Find the values of k for which x2+kx+4=0 has a double root.