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Chapter 9: Q39. (page 595)

Solve the equation by using the Quadratic formula. Round to the nearest tenth if necessary.

21x2+5x鈭�7=0

Short Answer

Expert verified

Thesolutions of the quadratic equations are 0.47 and-0.71.

Step by step solution

01

Step 1. Understand the concept used.

If ax2+bx+c=0, with a鈮�0, then x=鈭�b卤b2鈭�4ac2a. Solving using factoring can be done by splitting the middle term of the equation and then making groups and equating them to zero.

02

Step 2. Substitute the values. 

It is given that 21x2+5x鈭�7=0.Using the quadratic formula x=鈭�b卤b2鈭�4ac2a, substitute 21 for a,5for b and -7for c.

Put the values in the formula and get x=鈭�5卤52鈭�4脳21脳鈭�7221.

03

Step 3. Write the solutions.

Simplify the expression for x.

x=鈭�5卤52鈭�4脳21脳鈭�7221

=鈭�5卤25+58842=鈭�5卤61342=鈭�5卤24.7642

Therefore, either

role="math" localid="1647851783490" x=鈭�5+24.7642=0.47

or,

x=鈭�5鈭�24.7642=鈭�0.71

that is., either x=0.47or x=鈭�0.71.

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