I don't understand what you mean by 'mentally' but anyways, here is how to solve it.
(z−12)(z+12)
=(z+−12)(z+12)
=(z)(z)+(z)(12)+(−12)(z)+(−12)(12)
=z^2+12z−12z−144
=z^2−144
Answer:
- Find the coefficients using ax^2 + bx + c = 0
a = 4
b = 7
c = 0
- Make the coefficient equal 1. But how do we do that? Division.
4n² + 7n = 0
4/4n² + 7n/4 = 0/4
= n² + 7/4n = 0
a = 1
b = 7/4
c = 0
- Complete the square using b/2².
b = 7/4
(b/2)² = (7/4 ÷ 2)²
Use fraction rule.
7/4 ÷ 2² = 7/4² / 2²
<em>square the numbers</em>
7/4² / 2² = 49/16 ÷ 4
49/16 ÷ 4 = 49/16 × 1/4
49/16 × 1/4 = 49/64
Add to both sides of the equation using 49/64
b = 7/4
b/2 = 7/4 ÷ 2
<em>simplify</em>
b/2 = 7 ÷ (4 × 2)
<em>simplify(arithmetic)</em>
b/2 = 7/8
n² + 7/4n + 49/64 = 49/64
(n + 7/8)² = 49/64
Next, cancel out the square on the left side.
Subtract 7/8 from both of the sides.
Simplify the left side.
<em>That wraps it up for this equation. Hope it helped!</em>
Well it is definately not c haha. I would say 3 because it is a pretty even chance of getting three.
15 x 3/5
Cross out 15 and 5 . Divide by 5 .
15/5=3
3/3=1
3*3/1
3*3=9
Answer: 9