SOLUTION: when √(2z+1)+√(3z+4)= 7 the value of z is given by

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Question 896267: when √(2z+1)+√(3z+4)= 7 the value of z is given by
Answer by Edwin McCravy(20060) About Me  (Show Source):
You can put this solution on YOUR website!
sqrt%282z%2B1%29%2Bsqrt%283z%2B4%29%22%22=%22%227

Isolate one of the radical terms

sqrt%283z%2B4%29%22%22=%22%227%22%22-%22%22sqrt%282z%2B1%29

We square both sides:

%28sqrt%283z%2B4%29%29%5E2%22%22=%22%22%287-sqrt%282z%2B1%29%29%5E2

Squaring the square root on the left takes away the radical:
Write the right side twice multiplied by itself, so we can use FOIL:

3z%2B4%22%22=%22%22%287-sqrt%282z%2B1%29%29%287-sqrt%282z%2B1%29%29

3z%2B4%22%22=%22%2249-7sqrt%282z%2B1%29-7sqrt%282z%2B1%29%2B2z%2B1

Combine the radical terms on the right

3z%2B4%22%22=%22%2250-14sqrt%282z%2B1%29%2B2z

Isolate the radical term on the left

14sqrt%282z%2B1%29%22%22=%22%2246-z

Square both sides:

196%282x%2B1%29%22%22=%22%22%2846-z%29%5E2

392z%2B196%22%22=%22%222116-92z%2Bz%5E2

%220%22%22%22=%22%22z%5E2-484z%2B1920

Factor the right side:

%220%22%22%22=%22%22%28z-4%29%28z-480%29

Use the zero factor property:

        z - 4 = 0;   z-480 = 0
            z = 4;       z = 480

We must always check radical equations with square
or even roots for extraneous solutions:

Checking z=4
sqrt%282z%2B1%29%2Bsqrt%283z%2B4%29%22%22=%22%227
sqrt%282%284%29%2B1%29%2Bsqrt%283%284%29%2B4%29%22%22=%22%227
sqrt%288%2B1%29%2Bsqrt%2812%2B4%29%22%22=%22%227
sqrt%289%29%2Bsqrt%2816%29%22%22=%22%227
3%2B4%22%22=%22%227
7%22%22=%22%227



So 4 is a solution.

Checking x=480
sqrt%282z%2B1%29%2Bsqrt%283z%2B4%29%22%22=%22%227
sqrt%282%28480%29%2B1%29%2Bsqrt%283%28480%29%2B4%29%22%22=%22%227
sqrt%28960%2B1%29%2Bsqrt%281440%2B4%29%22%22=%22%227
sqrt%28961%29%2Bsqrt%281441%29%22%22=%22%227
31%2B38%22%22=%22%227
69%22%22=%22%227

So 480 is an extraneous answer, not a solution.

The only solution is z = 4

Edwin