sjschulz
24

# he steps to derive the quadratic formula are shown below: Step 1 ax2 + bx + c = 0 Step 2 ax2 + bx = - c Step 3 x2 + b over a times x equals negative c over a Step 4x2 + b over a times x plus b squared over 4 times a squared equals negative c over a Step 5 x2 + b over a times x plus b squared over 4 times a squared equals negative 4 multiplied by a multiplied by c, all over 4 multiplied by a squared plus b squared over 4 times a squared Step 6 the square of the quantity x plus b over 2 times a equals b squared minus 4 multiplied by a multiplied by c, all over 4 times a squared Step 7 x plus b over 2 times a equals plus or minus square root of the quantity b squared minus 4 times a times c over 4 times a squared equals plus or minus square root of b squared minus 4 times a times c, all divided by 2 times a Step 8 x = -negative b over 2 times a plus or minus square root of b squared minus 4 times a times c, all divided by 2 times a Step 9 x = negative b plus or minus square root of b squared minus 4 times a times c, all divided by 2 times a Which of the following is the first incorrect step? A. Step 4 B. Step 6 C. Step 7 D. Step 8

imma translate all the steps into numbers so it's easier to see and the reason we got to that step 1. $ax^2+bx+c=0$ given 2. $ax^2+bx=-c$ minus c from both sides 3. $x^2+\frac{b}{a}=\frac{-c}{a}$ divide both sides by a 4. $x^2+\frac{bx}{a}+\frac{b^2}{4a^2}=\frac{-c}{a}$ add $\frac{b^2}{4a^2}$ to both sides, wait, we didn't add it to both sides, only the left side, MISTAKE! so step 4 is wrong step